Is He Living,or Is He Dead is a splendid sample of Twain' s bitter satire.By focusing on textual analysis of the story,this thesis is trying to illustrate "surviving by dying",such a paradox of life impl...Is He Living,or Is He Dead is a splendid sample of Twain' s bitter satire.By focusing on textual analysis of the story,this thesis is trying to illustrate "surviving by dying",such a paradox of life implied by Mark Twain,and to reveal the tragic nature masked by the humorous satire in the story.展开更多
As I Lay Dying is one of Faulkner' s greatest works and an important novel of the Yoknapatawpha Saga.This thesis deals with the black humor in As I Lay Dying,as the humor contributes to a better understanding of c...As I Lay Dying is one of Faulkner' s greatest works and an important novel of the Yoknapatawpha Saga.This thesis deals with the black humor in As I Lay Dying,as the humor contributes to a better understanding of characterization,action,and theme of this fiction and Faulkner' s others.Eventually,we would realize that this fiction not only touches something in the American south but also the prob lems of all of the human beings.展开更多
Objective: Nurses play important roles in caring for dying patients and their families. Difficulties students confronted when facing dying patients challenge the quality of nursing education. A better understanding of...Objective: Nurses play important roles in caring for dying patients and their families. Difficulties students confronted when facing dying patients challenge the quality of nursing education. A better understanding of students' experiences would enhance teachers' ability in helping students. This study aims to describe available evidence about nursing students' experiences when caring for dying patients and their families.Methods: A review of qualitative studies published between 2005 and 2017 was undertaken using the following databases: MEDLINE, CINAHL, ProQuest Central, ScienceDirect, and CNKI. The keywords included were nursing students, experience, care, end-of-life, and dying. Qualitative Assessment and Review Instrument was used to assess the quality of the studies by two independent reviewers. The data from the studies were analyzed by meta-synthesis.Results: Eighteen English and two Chinese studies were selected in this review. Four themes were emerged:(1) Students with dying patients: students did not have enough ability in symptoms control, comfort supply, and therapeutic communication for dying patients.(2) Students with the patients' families: students advocated more caring for patients' families.(3) Students with the surroundings: professional medical staffs, especially the nursing preceptors, were key roles in constructing a supporting system for students.(4) Students with themselves: nursing students underwent various negative feelings and adopted both negative and positive strategies to cope with such feelings;students experienced professional and personal development during the caring for dying patients.Conclusions: Nursing students' abilities in terminal symptom control, comfort supply, and therapeutic communication should be improved by more theoretic learning and simulation practice. The nursing preceptors were key roles in constructing a supporting system for students and helping them to control the negative emotions when facing dying patients.展开更多
In this paper, we shall describe the way in which some Vietnamese people cope with death and dying. Authors surveyed approximately 302 relative people in the north of Vietnam. The sample showed broad demographic varia...In this paper, we shall describe the way in which some Vietnamese people cope with death and dying. Authors surveyed approximately 302 relative people in the north of Vietnam. The sample showed broad demographic variation. Among respondents, 73% were female and 27% were male. The instrument shows a good reliability of the total scores (Cronbach’s α= 0.93). Both exploratory factor analysis and confirmatory factor analysis are used. The model tested was a relatively simple model with three latent factors. They are belief, fear, and ritual and all of them are positive correlated. The relationships among factors are further analyzed and the mediating relationships are found.展开更多
Background: Caregivers experience problems when caring for people with intellectual disabilities who are terminally ill. Aim: The aim of this study is to gain a deeper understanding of the experience of the caregiver ...Background: Caregivers experience problems when caring for people with intellectual disabilities who are terminally ill. Aim: The aim of this study is to gain a deeper understanding of the experience of the caregiver when caring for a person with intellectual disabilities who is terminally ill and what influences this experience. Design: A qualitative research was carried out following the principles of Grounded Theory (GT) method, through fifteen interviews with caregivers in a living facility with continuous care. Results: The results show how caregivers strive to create meaningful moments for their client during the last period of his life. Since very few of the clients can clearly express their wishes and feelings, continuous observation is required of the caregivers for the interpretation of small signals of their clients. In that way, the appropriateness of their actions can be made certain. The results show that because of their involvement, caregivers are able to recognize clients’ signals. When a client is dying, the special atmosphere created on the ward contributes to coping with the situation and a positive experience. Conclusion: Direct-caregivers caring for a client with an intellectual disability who is terminally ill, experience an intense period of insecurity and also a special period meaningful when caring a dying client with intellectual disabilities. Their relationship with the client makes them to be more able to strive for client’s comfort. The results also show that some factors such as enough staff, clear and open communication with the physician and support of the manager contribute to the quality of palliative care on the ward.展开更多
The Dying Patient Law is very controversial in Israel; there are opinions that the reason for the Law was to prevent the court from making decisions on the subject of end of life according to democratic principles. I ...The Dying Patient Law is very controversial in Israel; there are opinions that the reason for the Law was to prevent the court from making decisions on the subject of end of life according to democratic principles. I decided to do this study because I wanted to know if the legal principles of the Law are democratic as were the court rulings or they are only, or mostly, Jewish principles and meant to prevent a democratic ruling in the courts. The work is a review of the Law and the Dying Patient Committee discussions as well as the chairman's writings on the Law, critique articles, and a review of democratic and bioethical principles. In this project, I have seen that the underlying basis of the Dying Patient Law is Jewish principles and not democratic principles, although Israel is a declared democratic state. This law illustrates the problem in Israel being both a democratic and a Jewish state. It raises the question: What can be done to resolve the conflict between the Jewish principles and democratic and/or bioethical principles?展开更多
[Objective] The paper was to explore the optimum dosage and application pattern of Trichoderma harzianum for controlling Potato Verticillium wilt. [ Method] Two trials, sowing seed tubers in bacterial manure, sowing s...[Objective] The paper was to explore the optimum dosage and application pattern of Trichoderma harzianum for controlling Potato Verticillium wilt. [ Method] Two trials, sowing seed tubers in bacterial manure, sowing seed tubers in bacterial manure + root irrigation after seedling emergence, were conducted in the paper. [Result] T.harzianum could effectively control potato early dying and promote potato growth, thereby increasing potato yield. The control effects of sowing tuber in 300 times of bacterial manure + root irrigation with 300 times of conidia suspension after seedling emergence were ideal ; the highest control effect and the highest saved yield loss were 72.60% and 33.33%, respectively. [ Conclusion] The paper provides reference for field application of T. harzianum.展开更多
Cahuilla is a dying Indian language in Southern California, USA. It is actually not used in everyday conservation but remembered by some elderly people only. Since the 1960s it has been recorded and analyzed by severa...Cahuilla is a dying Indian language in Southern California, USA. It is actually not used in everyday conservation but remembered by some elderly people only. Since the 1960s it has been recorded and analyzed by several German scholars. This paper presents the history of research, major methods employed in its study and the current progress as well as remaining topics to be studied.展开更多
In this paper, I examine Apple Founder Steve Job's final words "Oh wow. Oh wow. Oh wow" as uttered to his half-Sister Mona Simpson as a framework to explore how pre-experiential linguistic, social, and ontological ...In this paper, I examine Apple Founder Steve Job's final words "Oh wow. Oh wow. Oh wow" as uttered to his half-Sister Mona Simpson as a framework to explore how pre-experiential linguistic, social, and ontological patterns shape and construct consciousness and expressions at the final moment of death. Final words of passage provide society with insight into the experience of being human in the transition from life to death, both in their limitations and in their potential for providing a continuous fluidity of transformation. Understanding how these final words are transconceptual experiences will encourage us to reflect on alternative interpretative possibilities sensitive to ontological and logical contexts of death and dying providing a holistic alternative framework which is more congruent with individual spiritual needs.展开更多
In the human body, the number of cells is tightlyre gulated. When cells are no longer needed, they commit suicide through a programmed cell death,called apoptosis. Massive amount of cell apoptosis takes place in devel...In the human body, the number of cells is tightlyre gulated. When cells are no longer needed, they commit suicide through a programmed cell death,called apoptosis. Massive amount of cell apoptosis takes place in developing tissues and even adult bodies.展开更多
Maternal deaths remain a huge challenge on the African continent PUT awareness of maternal health firmly in the mindset of Africans and it will go a long way to reduce the ongoing tragedy of maternal deaths on the con...Maternal deaths remain a huge challenge on the African continent PUT awareness of maternal health firmly in the mindset of Africans and it will go a long way to reduce the ongoing tragedy of maternal deaths on the continent. That’s the qualified opinion of Dr.Ngoga Eugene,head of Obstetrics and Gynecology Department at the referral Hospital in Kigali, Rwanda. "We[Africa]have a shortage of skilled personnel,and even the few who are qualified migrate for better pay to developed展开更多
In order to effectively reduce energy consumption and increase range mile,new energy vehicles represented by Tesla have greatly aroused the application of integrated magnesium(Mg)alloy die casting technology in automo...In order to effectively reduce energy consumption and increase range mile,new energy vehicles represented by Tesla have greatly aroused the application of integrated magnesium(Mg)alloy die casting technology in automobiles.Previously,the application of Mg alloys in automobiles,especially in automotive cockpit components,is quite extensive,while it has almost disappeared for a period of time due to its relatively high cost,causing a certain degree of information loss in the application technology of Mg alloy parts in automobiles.The rapid development of automotive technology has led to a higher requirement for the automotive components compared with those traditional one.Therefore,whatever the components themselves,or the Mg alloy materials and die casting process have to face an increasing challenge,needing to be upgraded.In addition,owing to its high integration characteristics,the application of Mg alloy die casting technology in large-sized and thin-walled automotive parts has inherent advantages and needs to be expanded urgently.Indeed,it necessitates exploring advance Mg alloys and new product structures and optimizing die casting processes.This article summarizes and analyzes the development status of thin-walled and large-sized die casting Mg alloy parts in passenger car cockpit and corresponding material selection methods,die casting processes as well as mold design techniques.Furthermore,this work will aid researchers in establishing a comprehensive understanding of the manufacture of thin-walled and large-sized die casting Mg alloy parts in automobile cockpit.It will also assist them in developing new Mg alloys with improved comprehensive performance and new processes to meet the high requirements for die casting automotive components.展开更多
In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollu...In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollution.At this point,aluminum syntactic foams(ASFs)are new-generation engineering composites and come into the upfront as a problem-solver.Owing to their features like low density,sufficient elongation,and perfect energy absorption ability,these advanced foams have been considerably seductive for many industrial sectors nowadays.In this study,an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay(PEC).Micro evaluations(optical and FESEM)reveal that there is a homogenous particle distribution in the foam samples,and inspections are compatible with the other ASF studies.Additionally,T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive responses.Attained results show that PEC particles can be an alternative to expensive hollow spheres used in the previous works.Besides,a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength.展开更多
The effect of slow shot speed on externally solidified crystal(ESC),porosity and tensile property in a newly developed high-pressure die-cast Al-Si alloy was investigated by optical microscopy(OM),scanning electron mi...The effect of slow shot speed on externally solidified crystal(ESC),porosity and tensile property in a newly developed high-pressure die-cast Al-Si alloy was investigated by optical microscopy(OM),scanning electron microscopy(SEM)and laboratory computed tomography(CT).Results showed that the newly developed AlSi9MnMoV alloy exhibited improved mechanical properties when compared to the AlSi10MnMg alloy.The AlSi9MnMoV alloy,which was designed with trace multicomponent additions,displays a notable grain refining effect in comparison to the AlSi10MnMg alloy.Refining elements Ti,Zr,V,Nb,B promote heterogeneous nucleation and reduce the grain size of primaryα-Al.At a lower slow shot speed,the large ESCs are easier to form and gather,developing into the dendrite net and net-shrinkage.With an increase in slow shot speed,the size and number of ESCs and porosities significantly reduce.In addition,the distribution of ESCs is more dispersed and the net-shrinkage disappears.The tensile property is greatly improved by adopting a higher slow shot speed.The ultimate tensile strength is enhanced from 260.31 MPa to 290.31 MPa(increased by 11.52%),and the elongation is enhanced from 3.72%to 6.34%(increased by 70.52%).展开更多
Al and Mg alloy high pressure die castings(HPDC)are increasingly used in automotive industries.The microstructures in the castings have decisive effect on the casting mechanical properties,in which the microstructure ...Al and Mg alloy high pressure die castings(HPDC)are increasingly used in automotive industries.The microstructures in the castings have decisive effect on the casting mechanical properties,in which the microstructure characteristics are fundamental for the investigation of the microstructure-property relation.During the past decade,the microstructure characteristics of HPDC Al and Mg alloys,especially micro-pores andα-Fe,have been investigated from two-dimensional(2D)to threedimensional with X-ray micro-computed tomography(μ-CT).This paper provides an overview of the current understanding regarding the 3D characteristics and formation mechanisms of microstructures in HPDC alloys,their spatial distributions,and the impact on mechanical properties.Additionally,it outlines future research directions for the formation and control of heterogeneous microstructures in HPDC alloys.展开更多
Considering the components produced by high pressure die casting(HPDC)process usually with ultra-large sizes and complex morphologies,high temperature solid solution treatment is not a suitable method to further impro...Considering the components produced by high pressure die casting(HPDC)process usually with ultra-large sizes and complex morphologies,high temperature solid solution treatment is not a suitable method to further improve their mechanical properties.In this study,two-stage aging treatment with different pre-aging times was designed and employed to further improve the mechanical properties of HPDC Al8SiMgCuZn alloy.The characteristics of precipitates were evaluated by a transmission electron microscope(TEM),and the precipitation strengthening mechanism was discussed.The results reveal that the strengthening is mainly contributed by the precipitation ofβ″phase after two-stage aging,and the number density and size of the precipitates are significantly depended on the pre-aging time.The number density of precipitates is increased with the pre-aging time prolonged from 0 h to 4 h,and then decreases with the further increase of pre-aging time from 4 h to 6 h.The precipitates with the highest density and smallest size are observed after pre-aging for 4 h.After pre-aged at 100℃for 4 h and then artificial aged at 200℃for 30 min,the yield strength of 207 MPa,ultimate tensile strength of 325 MPa and elongation of 7.6%are achieved.展开更多
Magnesium alloy is one of the lightest metal structural materials.The weight is further reduced through the hollow structure.However,the hollow structure is easily damaged during processing.In order to maintain the ho...Magnesium alloy is one of the lightest metal structural materials.The weight is further reduced through the hollow structure.However,the hollow structure is easily damaged during processing.In order to maintain the hollow structure and to transfer the stresses during the high temperature deformation,the sand mandrel is proposed.In this paper,the hollow AZ31 magnesium alloy three-channel joint is studied by hot extrusion forming.Sand as one of solid granule medium is used to fill the hollow magnesium alloy.The extrusion temperatures are 230℃ and 300℃,respectively.The process parameters(die angle,temperature,bottom thickness,sidewall thickness,edge-to-middle ratio in bottom,bottom shape)of the hollow magnesium alloy are analyzed based on the results of experiments and the finite element method.The results are shown that the formability of the hollow magnesium alloy will be much better when the ratio of sidewall thickness to the bottom thickness is 1:1.5.Also when edge-to-middle ratio in bottom is about 1:1.5,a better forming product can be received.The best bottom shape in these experiments will be convex based on the forming results.The grain will be refined obviously after the extrusion.Also the microstructures will be shown as streamlines.And these lines will be well agreement with the mold in the corner.展开更多
文摘Is He Living,or Is He Dead is a splendid sample of Twain' s bitter satire.By focusing on textual analysis of the story,this thesis is trying to illustrate "surviving by dying",such a paradox of life implied by Mark Twain,and to reveal the tragic nature masked by the humorous satire in the story.
文摘As I Lay Dying is one of Faulkner' s greatest works and an important novel of the Yoknapatawpha Saga.This thesis deals with the black humor in As I Lay Dying,as the humor contributes to a better understanding of characterization,action,and theme of this fiction and Faulkner' s others.Eventually,we would realize that this fiction not only touches something in the American south but also the prob lems of all of the human beings.
基金supported by the Macao Science and Technology Development Fund(No.FDCT 276/2017/P)
文摘Objective: Nurses play important roles in caring for dying patients and their families. Difficulties students confronted when facing dying patients challenge the quality of nursing education. A better understanding of students' experiences would enhance teachers' ability in helping students. This study aims to describe available evidence about nursing students' experiences when caring for dying patients and their families.Methods: A review of qualitative studies published between 2005 and 2017 was undertaken using the following databases: MEDLINE, CINAHL, ProQuest Central, ScienceDirect, and CNKI. The keywords included were nursing students, experience, care, end-of-life, and dying. Qualitative Assessment and Review Instrument was used to assess the quality of the studies by two independent reviewers. The data from the studies were analyzed by meta-synthesis.Results: Eighteen English and two Chinese studies were selected in this review. Four themes were emerged:(1) Students with dying patients: students did not have enough ability in symptoms control, comfort supply, and therapeutic communication for dying patients.(2) Students with the patients' families: students advocated more caring for patients' families.(3) Students with the surroundings: professional medical staffs, especially the nursing preceptors, were key roles in constructing a supporting system for students.(4) Students with themselves: nursing students underwent various negative feelings and adopted both negative and positive strategies to cope with such feelings;students experienced professional and personal development during the caring for dying patients.Conclusions: Nursing students' abilities in terminal symptom control, comfort supply, and therapeutic communication should be improved by more theoretic learning and simulation practice. The nursing preceptors were key roles in constructing a supporting system for students and helping them to control the negative emotions when facing dying patients.
文摘In this paper, we shall describe the way in which some Vietnamese people cope with death and dying. Authors surveyed approximately 302 relative people in the north of Vietnam. The sample showed broad demographic variation. Among respondents, 73% were female and 27% were male. The instrument shows a good reliability of the total scores (Cronbach’s α= 0.93). Both exploratory factor analysis and confirmatory factor analysis are used. The model tested was a relatively simple model with three latent factors. They are belief, fear, and ritual and all of them are positive correlated. The relationships among factors are further analyzed and the mediating relationships are found.
文摘Background: Caregivers experience problems when caring for people with intellectual disabilities who are terminally ill. Aim: The aim of this study is to gain a deeper understanding of the experience of the caregiver when caring for a person with intellectual disabilities who is terminally ill and what influences this experience. Design: A qualitative research was carried out following the principles of Grounded Theory (GT) method, through fifteen interviews with caregivers in a living facility with continuous care. Results: The results show how caregivers strive to create meaningful moments for their client during the last period of his life. Since very few of the clients can clearly express their wishes and feelings, continuous observation is required of the caregivers for the interpretation of small signals of their clients. In that way, the appropriateness of their actions can be made certain. The results show that because of their involvement, caregivers are able to recognize clients’ signals. When a client is dying, the special atmosphere created on the ward contributes to coping with the situation and a positive experience. Conclusion: Direct-caregivers caring for a client with an intellectual disability who is terminally ill, experience an intense period of insecurity and also a special period meaningful when caring a dying client with intellectual disabilities. Their relationship with the client makes them to be more able to strive for client’s comfort. The results also show that some factors such as enough staff, clear and open communication with the physician and support of the manager contribute to the quality of palliative care on the ward.
文摘The Dying Patient Law is very controversial in Israel; there are opinions that the reason for the Law was to prevent the court from making decisions on the subject of end of life according to democratic principles. I decided to do this study because I wanted to know if the legal principles of the Law are democratic as were the court rulings or they are only, or mostly, Jewish principles and meant to prevent a democratic ruling in the courts. The work is a review of the Law and the Dying Patient Committee discussions as well as the chairman's writings on the Law, critique articles, and a review of democratic and bioethical principles. In this project, I have seen that the underlying basis of the Dying Patient Law is Jewish principles and not democratic principles, although Israel is a declared democratic state. This law illustrates the problem in Israel being both a democratic and a Jewish state. It raises the question: What can be done to resolve the conflict between the Jewish principles and democratic and/or bioethical principles?
基金Supported by Science and Technology Project of Guizhou Province[QKHN G(2007)4007]Project of Guizhou Academy of Agricultural Sciences[QNKH(Key)08017]
文摘[Objective] The paper was to explore the optimum dosage and application pattern of Trichoderma harzianum for controlling Potato Verticillium wilt. [ Method] Two trials, sowing seed tubers in bacterial manure, sowing seed tubers in bacterial manure + root irrigation after seedling emergence, were conducted in the paper. [Result] T.harzianum could effectively control potato early dying and promote potato growth, thereby increasing potato yield. The control effects of sowing tuber in 300 times of bacterial manure + root irrigation with 300 times of conidia suspension after seedling emergence were ideal ; the highest control effect and the highest saved yield loss were 72.60% and 33.33%, respectively. [ Conclusion] The paper provides reference for field application of T. harzianum.
文摘Cahuilla is a dying Indian language in Southern California, USA. It is actually not used in everyday conservation but remembered by some elderly people only. Since the 1960s it has been recorded and analyzed by several German scholars. This paper presents the history of research, major methods employed in its study and the current progress as well as remaining topics to be studied.
文摘In this paper, I examine Apple Founder Steve Job's final words "Oh wow. Oh wow. Oh wow" as uttered to his half-Sister Mona Simpson as a framework to explore how pre-experiential linguistic, social, and ontological patterns shape and construct consciousness and expressions at the final moment of death. Final words of passage provide society with insight into the experience of being human in the transition from life to death, both in their limitations and in their potential for providing a continuous fluidity of transformation. Understanding how these final words are transconceptual experiences will encourage us to reflect on alternative interpretative possibilities sensitive to ontological and logical contexts of death and dying providing a holistic alternative framework which is more congruent with individual spiritual needs.
基金supported by the National Natural Science Foundation of Chinathe Ministry of Science and Technology of ChinaCAS
文摘In the human body, the number of cells is tightlyre gulated. When cells are no longer needed, they commit suicide through a programmed cell death,called apoptosis. Massive amount of cell apoptosis takes place in developing tissues and even adult bodies.
文摘Maternal deaths remain a huge challenge on the African continent PUT awareness of maternal health firmly in the mindset of Africans and it will go a long way to reduce the ongoing tragedy of maternal deaths on the continent. That’s the qualified opinion of Dr.Ngoga Eugene,head of Obstetrics and Gynecology Department at the referral Hospital in Kigali, Rwanda. "We[Africa]have a shortage of skilled personnel,and even the few who are qualified migrate for better pay to developed
基金supported by the foundation of“Cold area new energy service engineering laboratory battery pack comprehensive test system”from Jilin Provincial Development and Reform Commission(2020C021-6)the National Natural Science Foundation of China(NNSFC,No.52371109).
文摘In order to effectively reduce energy consumption and increase range mile,new energy vehicles represented by Tesla have greatly aroused the application of integrated magnesium(Mg)alloy die casting technology in automobiles.Previously,the application of Mg alloys in automobiles,especially in automotive cockpit components,is quite extensive,while it has almost disappeared for a period of time due to its relatively high cost,causing a certain degree of information loss in the application technology of Mg alloy parts in automobiles.The rapid development of automotive technology has led to a higher requirement for the automotive components compared with those traditional one.Therefore,whatever the components themselves,or the Mg alloy materials and die casting process have to face an increasing challenge,needing to be upgraded.In addition,owing to its high integration characteristics,the application of Mg alloy die casting technology in large-sized and thin-walled automotive parts has inherent advantages and needs to be expanded urgently.Indeed,it necessitates exploring advance Mg alloys and new product structures and optimizing die casting processes.This article summarizes and analyzes the development status of thin-walled and large-sized die casting Mg alloy parts in passenger car cockpit and corresponding material selection methods,die casting processes as well as mold design techniques.Furthermore,this work will aid researchers in establishing a comprehensive understanding of the manufacture of thin-walled and large-sized die casting Mg alloy parts in automobile cockpit.It will also assist them in developing new Mg alloys with improved comprehensive performance and new processes to meet the high requirements for die casting automotive components.
文摘In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollution.At this point,aluminum syntactic foams(ASFs)are new-generation engineering composites and come into the upfront as a problem-solver.Owing to their features like low density,sufficient elongation,and perfect energy absorption ability,these advanced foams have been considerably seductive for many industrial sectors nowadays.In this study,an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay(PEC).Micro evaluations(optical and FESEM)reveal that there is a homogenous particle distribution in the foam samples,and inspections are compatible with the other ASF studies.Additionally,T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive responses.Attained results show that PEC particles can be an alternative to expensive hollow spheres used in the previous works.Besides,a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength.
基金financially supported by the National Key Research and Development Program of China(2022YFB3404201)the Major Science and Technology Project of Changchun City,Jilin Province(Grant No.20210301024GX)。
文摘The effect of slow shot speed on externally solidified crystal(ESC),porosity and tensile property in a newly developed high-pressure die-cast Al-Si alloy was investigated by optical microscopy(OM),scanning electron microscopy(SEM)and laboratory computed tomography(CT).Results showed that the newly developed AlSi9MnMoV alloy exhibited improved mechanical properties when compared to the AlSi10MnMg alloy.The AlSi9MnMoV alloy,which was designed with trace multicomponent additions,displays a notable grain refining effect in comparison to the AlSi10MnMg alloy.Refining elements Ti,Zr,V,Nb,B promote heterogeneous nucleation and reduce the grain size of primaryα-Al.At a lower slow shot speed,the large ESCs are easier to form and gather,developing into the dendrite net and net-shrinkage.With an increase in slow shot speed,the size and number of ESCs and porosities significantly reduce.In addition,the distribution of ESCs is more dispersed and the net-shrinkage disappears.The tensile property is greatly improved by adopting a higher slow shot speed.The ultimate tensile strength is enhanced from 260.31 MPa to 290.31 MPa(increased by 11.52%),and the elongation is enhanced from 3.72%to 6.34%(increased by 70.52%).
基金supported by the National Natural Science Foundation of China(Nos.51875211 and 51375171)Beijing Natural Science Foundation(No.L223001)+1 种基金Natural Science Foundation of Guangdong Province(No.2023A1515012730)the Program for New Century Excellent Talents in University in China(No.NCET-08-0209).
文摘Al and Mg alloy high pressure die castings(HPDC)are increasingly used in automotive industries.The microstructures in the castings have decisive effect on the casting mechanical properties,in which the microstructure characteristics are fundamental for the investigation of the microstructure-property relation.During the past decade,the microstructure characteristics of HPDC Al and Mg alloys,especially micro-pores andα-Fe,have been investigated from two-dimensional(2D)to threedimensional with X-ray micro-computed tomography(μ-CT).This paper provides an overview of the current understanding regarding the 3D characteristics and formation mechanisms of microstructures in HPDC alloys,their spatial distributions,and the impact on mechanical properties.Additionally,it outlines future research directions for the formation and control of heterogeneous microstructures in HPDC alloys.
基金financially supported by the Natural Science Foundation of Guangdong Province(Nos.2021A151510042,2021A1515011728)the China Postdoctoral Science Foundation(2022M711190)+1 种基金the National Natural Science Foundation of China(No.51875211)the Key Area Research and Development Program of Guangdong Province(No.2020B010186002)。
文摘Considering the components produced by high pressure die casting(HPDC)process usually with ultra-large sizes and complex morphologies,high temperature solid solution treatment is not a suitable method to further improve their mechanical properties.In this study,two-stage aging treatment with different pre-aging times was designed and employed to further improve the mechanical properties of HPDC Al8SiMgCuZn alloy.The characteristics of precipitates were evaluated by a transmission electron microscope(TEM),and the precipitation strengthening mechanism was discussed.The results reveal that the strengthening is mainly contributed by the precipitation ofβ″phase after two-stage aging,and the number density and size of the precipitates are significantly depended on the pre-aging time.The number density of precipitates is increased with the pre-aging time prolonged from 0 h to 4 h,and then decreases with the further increase of pre-aging time from 4 h to 6 h.The precipitates with the highest density and smallest size are observed after pre-aging for 4 h.After pre-aged at 100℃for 4 h and then artificial aged at 200℃for 30 min,the yield strength of 207 MPa,ultimate tensile strength of 325 MPa and elongation of 7.6%are achieved.
基金National Natural Science Foundation of China No.51905068Natural Science Foundation of Liaoning Province No.2020-HYLH-24The open research fund from the State Key Laboratory of Rolling and Automation,Northeastern University No.2020RALKFKT012。
文摘Magnesium alloy is one of the lightest metal structural materials.The weight is further reduced through the hollow structure.However,the hollow structure is easily damaged during processing.In order to maintain the hollow structure and to transfer the stresses during the high temperature deformation,the sand mandrel is proposed.In this paper,the hollow AZ31 magnesium alloy three-channel joint is studied by hot extrusion forming.Sand as one of solid granule medium is used to fill the hollow magnesium alloy.The extrusion temperatures are 230℃ and 300℃,respectively.The process parameters(die angle,temperature,bottom thickness,sidewall thickness,edge-to-middle ratio in bottom,bottom shape)of the hollow magnesium alloy are analyzed based on the results of experiments and the finite element method.The results are shown that the formability of the hollow magnesium alloy will be much better when the ratio of sidewall thickness to the bottom thickness is 1:1.5.Also when edge-to-middle ratio in bottom is about 1:1.5,a better forming product can be received.The best bottom shape in these experiments will be convex based on the forming results.The grain will be refined obviously after the extrusion.Also the microstructures will be shown as streamlines.And these lines will be well agreement with the mold in the corner.