One orbit flip and two inclination flips bifurcation is considered with resonant principal eigenvalues. We introduce a local active coordinate system to establish bifurcation equation and obtain the conditions when th...One orbit flip and two inclination flips bifurcation is considered with resonant principal eigenvalues. We introduce a local active coordinate system to establish bifurcation equation and obtain the conditions when the original homoclinic orbit is kept or broken. We also prove the existence and the existence regions of double 1-periodic orbit bifurcation. Moreover, the complicated homoclinic-doubling bifurcations are found and expressed approximately, and are well located.展开更多
Polymorphisms in promoter regions of inflammatory cytokines have been widely studied,and potentially functional polymorphisms have been discovered.Conflicting results from meta-analyses of interleukin(IL)-1B and IL-10...Polymorphisms in promoter regions of inflammatory cytokines have been widely studied,and potentially functional polymorphisms have been discovered.Conflicting results from meta-analyses of interleukin(IL)-1B and IL-10 polymorphisms show differences in gastric cancer susceptibilities between Caucasian and Asian populations.In particular,we note the suggestion of an allele flip in IL-1B and IL-10 gene polymorphisms.In Asian populations,the IL-1B-1464G/-511C/-31T haplotype indicates risk for gastric cancer,while the opposite haplotype,IL-1B-1464C/-511T/-31C is the risk-related allele in Caucasians.Furthermore,while IL-10-1082G/-819C/-592C is associated with gastric cancer in Asians,IL-10-1082A/-819T/-592T is linked to gastric cancer risk in Caucasians.These seemingly contradictory results may be attributed to distinct carcinogenic mechanisms underlying the different gastric cancer subtypes.The allele flip observed in IL-10 and gastric cancer appears to reflect allelic heterogeneity,similar to that observed in IL-1B.In this review,we focus on the allele flip phenomenon observed between different ethnic groups in an effort to resolve certain controversial results from recent studies on interleukin polymorphism.In addition,we re-emphasize the importance of stratifying gastric cancer subtypes based on anatomical site and Lauren classification to prevent false associations arising through dilution of true ones.展开更多
Homoclinic bifurcation with one orbit flip, two inclination flips and resonance in the tangent directions of homoclinic orbit is considered. By studying the associated successor functions constructed from a local acti...Homoclinic bifurcation with one orbit flip, two inclination flips and resonance in the tangent directions of homoclinic orbit is considered. By studying the associated successor functions constructed from a local active coordinate system, we prove the existence of double 1-periodic orbit, 1-homoclinic orbit, and also some coexistence conditions of 1-periodic orbit and 1-homoclinic orbit.展开更多
A high-codimension homoclinic bifurcation is considered with one orbit flip and two inclination flips accompanied by resonant principal eigenvalues. A local active coordinate system in a small neighborhood of homoclin...A high-codimension homoclinic bifurcation is considered with one orbit flip and two inclination flips accompanied by resonant principal eigenvalues. A local active coordinate system in a small neighborhood of homoclinic orbit is introduced. By analysis of the bifurcation equation, the authors obtain the conditions when the original flip homoclinic orbit is kept or broken. The existence and the existence regions of several double periodic orbits and one triple periodic orbit bifurcations are proved. Moreover, the complicated homoclinic-doubling bifurcations are found and expressed approximately.展开更多
In this paper, the heteroclinic bifurcation problem with real eigenvalues and two incli- nation-flips is investigated in a four-dimensional reversible system. We perform a detailed study of this case by using the meth...In this paper, the heteroclinic bifurcation problem with real eigenvalues and two incli- nation-flips is investigated in a four-dimensional reversible system. We perform a detailed study of this case by using the method originally established in the papers "Problems in Homoclinic Bifurcation with Higher Dimensions" and "Bifurcation of Heteroclinic Loops," and obtain fruitful results, such as the existence and coexistence of R-symmetric homoclinic orbit and R-symmetric heteroclinic loops, R-symmetric homoclinic orbit and R-symmetric periodic orbit. The double R-symmetric homoclinic bifurcation (i.e., two-fold R-symmetric homoclinic bifurcation) for reversible heteroclinic loops is found, and the existence of infinitely many R-symmetric periodic orbits accumulating onto a homoclinic orbit is demonstrated. The relevant bifurcation surfaces and the existence regions are also located.展开更多
Homoclinic bifurcations in four-dimensional vector fields are investigated by setting up a local coordinate near a homoclinic orbit. This homoclinic orbit is principal but its stable and unstable foliations take incli...Homoclinic bifurcations in four-dimensional vector fields are investigated by setting up a local coordinate near a homoclinic orbit. This homoclinic orbit is principal but its stable and unstable foliations take inclination flip. The existence, nonexistence, and uniqueness of the 1-homoclinic orbit and 1-periodic orbit are studied. The existence of the two-fold 1-periodic orbit and three-fold 1 -periodic orbit are also obtained. It is indicated that the number of periodic orbits bifurcated from this kind of homoclinic orbits depends heavily on the strength of the inclination flip.展开更多
The homoclinic bifurcations in four dimensional vector fields are investigated by setting up a local coordinates near the homoclinic orbit. This homoclinic orbit is nonprincipal in the meanings that its positive semi-...The homoclinic bifurcations in four dimensional vector fields are investigated by setting up a local coordinates near the homoclinic orbit. This homoclinic orbit is nonprincipal in the meanings that its positive semi-orbit takes orbit flip and its unstable foliation takes inclination flip. The existence, nonexistence, uniqueness and coexistence of the 1-homoclinic orbit and the 1-periodic orbit are studied. The existence of the twofold periodic orbit and three-fold periodic orbit are also obtained.展开更多
The paper studies a codimension-4 resonant homoclinic bifurcation with one orbit flip and two inclination flips, where the resonance takes place in the tangent direction of homoclinic orbit.Local active coordinate sys...The paper studies a codimension-4 resonant homoclinic bifurcation with one orbit flip and two inclination flips, where the resonance takes place in the tangent direction of homoclinic orbit.Local active coordinate system is introduced to construct the Poincar′e returning map, and also the associated successor functions. We prove the existence of the saddle-node bifurcation, the perioddoubling bifurcation and the homoclinic-doubling bifurcation, and also locate the corresponding 1-periodic orbit, 1-homoclinic orbit, double periodic orbits and some 2n-homoclinic orbits.展开更多
Flipped is a book written by American author Wendelin Van Draanen. It is a novel about young teenagers and was adapted into the famous film of the same name in 2010. The thesis employs speech acts, as pioneered by Joh...Flipped is a book written by American author Wendelin Van Draanen. It is a novel about young teenagers and was adapted into the famous film of the same name in 2010. The thesis employs speech acts, as pioneered by John Austin and further developed by John Searle, to investigate the influence of dialogues on characterization and plot development in Flipped. By exploring the theory of speech acts presented in dialogues between characters, the author deciphers the underlying intentions embodied in the dialogues and demonstrates the importance of the use of speech acts in dialogues in revealing the characters, driving the development of the plot and expressing the theme of the text.展开更多
Active rods propelled along their long axis align their velocities and orientations simultaneously in collision.However,as the propulsion is perpendicular to the long axis,velocity alignment becomes dynamically diffic...Active rods propelled along their long axis align their velocities and orientations simultaneously in collision.However,as the propulsion is perpendicular to the long axis,velocity alignment becomes dynamically difficult.Here,we show that ellipsoidal Quincke roller propelled along their short-axis(perpendicular to the long axis)can align their velocities by flipping and form flocking with nematic order.The flipping arises from the reversible transition between the static parallel spinless state and the spinning transversal state of ellipsoidal Quincke rollers.This is possible only near(above)the critical field where both the parallel spinless state and the spinning transversal spinning are metastable.The flipping-facilitated alignment offers an extra aligning mechanism for elongate active agents,and the resulting active liquid crystals serve a model system to explore the defect dynamics as the propulsion deviates from the local nematic orientation which has not been addressed yet.展开更多
Objective:To explore the application effect of group cooperative learning combined with flipped classroom in standardized training of emergency surgery resident physicians.Methods:95 resident physicians undergoing eme...Objective:To explore the application effect of group cooperative learning combined with flipped classroom in standardized training of emergency surgery resident physicians.Methods:95 resident physicians undergoing emergency surgery standardized training in our hospital were randomly divided into an experimental group(46,group cooperative learning+flipped classroom)and a control group(49,traditional teaching).The training period was 2 months.Results:The graduation assessment scores of the experimental group were higher than those of the control group(P<0.05).The improvement in critical thinking ability and self-learning ability was better than that of the control group(P<0.05).The response rate of“yes”to all items of course teaching satisfaction was significantly higher than that of the control group(P<0.05).The satisfaction scores for training teachers were higher than those of the control group(P<0.05).Conclusion:The teaching model of group cooperative learning combined with flipped classroom,through reconstructing the learning process and activating interactive participation,can significantly improve the clinical operation and theoretical foundation of emergency surgery standardized training students.It also cultivates core professional qualities such as critical thinking,self-learning,and team collaboration,providing a feasible paradigm for integrated medical education in this discipline.展开更多
Effect of flip chip bonding parameters on microstructure at the interconnect interface and shear properties of 64.8Sn35.2Pb microbumps were investigated in this work.Results show that the main intermetallic compound(I...Effect of flip chip bonding parameters on microstructure at the interconnect interface and shear properties of 64.8Sn35.2Pb microbumps were investigated in this work.Results show that the main intermetallic compound(IMC)at the interconnect interface is(Ni,Cu)_(3)Sn_(4)phase,and meanwhile a small amount of(Cu,Ni)_(6)Sn_(5)phase with a size of 50−100 nm is formed around(Ni,Cu)_(3)Sn_(4)phase.The orientation relationship of[-1-56](Ni,Cu)_(3)Sn_(4)//[152](Cu,Ni)_(6)Sn_(5)and(601)(Ni,Cu)_(3)Sn_(4)//(-201)(Cu,Ni)_(6)Sn_(5)is found between these two phases,and the atomic matching at the interface of the two phases is low.The highest shear force of 77.3 gf is achieved in the 64.8Sn35.2Pb microbump at the peak temperature of 250℃and parameter V1 because dense IMCs and no cracks form at the interconnect interface.Two typical fracture modes of microbumps are determined as solder fracture and mixed fracture.The high thermal stress presenting in the thick IMCs layer induces crack initiation,and cracks propagate along theα/βphase boundaries in the Sn-Pb solder under shear force,leading to a mixed fracture mode in the microbumps.展开更多
Flip-chip technology is widely used in integrated circuit(IC)packaging.Molded underfill transfer molding is the most common process for these products,as the chip and solder bumps must be protected by the encapsulatin...Flip-chip technology is widely used in integrated circuit(IC)packaging.Molded underfill transfer molding is the most common process for these products,as the chip and solder bumps must be protected by the encapsulating material to ensure good reliability.Flow-front merging usually occurs during the molding process,and air is then trapped under the chip,which can form voids in the molded product.The void under the chip may cause stability and reliability problems.However,the flow process is unobservable during the transfer molding process.The engineer can only check for voids in the molded product after the process is complete.Previous studies have used fluid visualization experiments and developed computational fluid dynamics simulation tools to investigate this issue.However,a critical gap remains in establishing a comprehensive three-dimensional model that integrates two-phase flow,accurate venting settings,and fluid surface tension for molded underfill void evaluation—validated by experimental fluid visualization.This study aims to address this gap in the existing literature.In this study,a fluid visualization experiment was designed to simulate the transfer molding process,allowing for the observation of flow-front merging and void formation behaviors.For comparison,a three-dimensional mold flow analysis was also performed.It was found that the numerical simulation of the trapped air compression process under the chip was more accurate when considering the capillary force.The effect of design factors is evaluated in this paper.The results show that the most important factors for void size are fluid viscosity,the gap height under the chip,transfer time,contact angle between the fluid and the contact surfaces,and transfer pressure.Specifically,a smaller gap height beneath the chip aggravates void formation,while lower viscosity,extended transfer time,reduced contact angle,and increased transfer pressure are effective in minimizing void size.The overall results of this study will be useful for product and process design in selecting appropriate solutions for IC packaging,particularly in the development of void-free molded-underfill flip-chip packages.These findings support the optimization of industrial packaging processes in semiconductor manufacturing by guiding material selection and process parameters,ultimately enhancing package reliability and yield.展开更多
Objective:To explore the application effect of an information-based flipped classroom teaching model in nursing education of rheumatology and immunology,providing empirical evidence for optimizing specialized nursing ...Objective:To explore the application effect of an information-based flipped classroom teaching model in nursing education of rheumatology and immunology,providing empirical evidence for optimizing specialized nursing education models.Methods:Eighty nursing students from the 2021 grade of Xi’an Medical University were selected as research subjects and randomly divided into an experimental group(n=40)and a control group(n=40)using a random number table method.The control group received traditional lecture-based teaching,while the experimental group underwent information-based flipped classroom teaching.The theoretical knowledge scores and practical operation assessment scores of the two groups were compared after teaching,and the teaching satisfaction of the experimental group students was evaluated through a questionnaire survey.Results:The theoretical knowledge score(85.60±5.20)and practical operation score(88.30±4.70)of the experimental group were significantly higher than those of the control group(76.20±6.50)and(75.80±5.90),respectively.The differences were statistically significant(p<0.05).The satisfaction scores of all dimensions in the experimental group were significantly higher than those in the control group,and the differences were statistically significant(p<0.05).Conclusion:The information-based flipped classroom teaching model can effectively improve the quality of nursing teaching in rheumatology and immunology,enhance students’knowledge mastery and practical abilities,and is worthy of promotion and application in clinical nursing teaching.展开更多
Objective:This study aimed to investigate the learning expectations of undergraduate nursing students regarding the flipped Health Assessment course.Methods:This descriptive,qualitative study was conducted at a medica...Objective:This study aimed to investigate the learning expectations of undergraduate nursing students regarding the flipped Health Assessment course.Methods:This descriptive,qualitative study was conducted at a medical university in Fuzhou,Fujian Province,China.An interview outline was designed based on the core dimensions of Expectation Confirmation Theory(expectation sources,expectation content,and expectation importance).Thirty second-year undergraduate nursing students who had completed first-year basic medical courses and were about to take the flipped Health Assessment course were interviewed between June and July 2022.Interview data were analyzed using qualitative content analysis.Results:Five major themes and thirteen subthemes were identified.Theme 1 was expectation sourcesperceived learning difficulties from past experiences,which included four subthemes:insufficient autonomous learning ability,confusion regarding learning methods,insufficient engagement in learning,and low professional identity.Theme 2 included knowledge and information expectations,which comprised three subthemes:knowledge to improve professional competence,knowledge to enhance academic competitiveness,and knowledge to boost self-efficacy.Theme 3 comprised logical expectations and included two subthemes:flexible teaching methods and efficient instructional tools.Theme 4,pleasure expectations,included two subthemes:vivid teaching styles and diversified teaching evaluations.Theme 5 comprised professional value expectations and included two subthemes:teachers'responsible professional attitudes and gentle emotional support.Conclusion:Students'learning expectations originate from perceived learning difficulties,such as insufficient learning autonomy and engagement,confusion about learning methods,and a lack of professional identity.They showed various learning expectations for the flipped Health Assessment course,including knowledge and information,logic,pleasure,and professional value expectations.展开更多
文摘One orbit flip and two inclination flips bifurcation is considered with resonant principal eigenvalues. We introduce a local active coordinate system to establish bifurcation equation and obtain the conditions when the original homoclinic orbit is kept or broken. We also prove the existence and the existence regions of double 1-periodic orbit bifurcation. Moreover, the complicated homoclinic-doubling bifurcations are found and expressed approximately, and are well located.
文摘Polymorphisms in promoter regions of inflammatory cytokines have been widely studied,and potentially functional polymorphisms have been discovered.Conflicting results from meta-analyses of interleukin(IL)-1B and IL-10 polymorphisms show differences in gastric cancer susceptibilities between Caucasian and Asian populations.In particular,we note the suggestion of an allele flip in IL-1B and IL-10 gene polymorphisms.In Asian populations,the IL-1B-1464G/-511C/-31T haplotype indicates risk for gastric cancer,while the opposite haplotype,IL-1B-1464C/-511T/-31C is the risk-related allele in Caucasians.Furthermore,while IL-10-1082G/-819C/-592C is associated with gastric cancer in Asians,IL-10-1082A/-819T/-592T is linked to gastric cancer risk in Caucasians.These seemingly contradictory results may be attributed to distinct carcinogenic mechanisms underlying the different gastric cancer subtypes.The allele flip observed in IL-10 and gastric cancer appears to reflect allelic heterogeneity,similar to that observed in IL-1B.In this review,we focus on the allele flip phenomenon observed between different ethnic groups in an effort to resolve certain controversial results from recent studies on interleukin polymorphism.In addition,we re-emphasize the importance of stratifying gastric cancer subtypes based on anatomical site and Lauren classification to prevent false associations arising through dilution of true ones.
文摘Homoclinic bifurcation with one orbit flip, two inclination flips and resonance in the tangent directions of homoclinic orbit is considered. By studying the associated successor functions constructed from a local active coordinate system, we prove the existence of double 1-periodic orbit, 1-homoclinic orbit, and also some coexistence conditions of 1-periodic orbit and 1-homoclinic orbit.
基金supported by the National Natural Science Foundation of China(No.11126097)
文摘A high-codimension homoclinic bifurcation is considered with one orbit flip and two inclination flips accompanied by resonant principal eigenvalues. A local active coordinate system in a small neighborhood of homoclinic orbit is introduced. By analysis of the bifurcation equation, the authors obtain the conditions when the original flip homoclinic orbit is kept or broken. The existence and the existence regions of several double periodic orbits and one triple periodic orbit bifurcations are proved. Moreover, the complicated homoclinic-doubling bifurcations are found and expressed approximately.
基金supported by National Natural Science Foundation of China (Grant No. 10671069)
文摘In this paper, the heteroclinic bifurcation problem with real eigenvalues and two incli- nation-flips is investigated in a four-dimensional reversible system. We perform a detailed study of this case by using the method originally established in the papers "Problems in Homoclinic Bifurcation with Higher Dimensions" and "Bifurcation of Heteroclinic Loops," and obtain fruitful results, such as the existence and coexistence of R-symmetric homoclinic orbit and R-symmetric heteroclinic loops, R-symmetric homoclinic orbit and R-symmetric periodic orbit. The double R-symmetric homoclinic bifurcation (i.e., two-fold R-symmetric homoclinic bifurcation) for reversible heteroclinic loops is found, and the existence of infinitely many R-symmetric periodic orbits accumulating onto a homoclinic orbit is demonstrated. The relevant bifurcation surfaces and the existence regions are also located.
基金This paper was completed when the first author was visiting East China Normal University.This work was supported by the National Natural Science Foundation of China(Grant No.10071022).
文摘Homoclinic bifurcations in four-dimensional vector fields are investigated by setting up a local coordinate near a homoclinic orbit. This homoclinic orbit is principal but its stable and unstable foliations take inclination flip. The existence, nonexistence, and uniqueness of the 1-homoclinic orbit and 1-periodic orbit are studied. The existence of the two-fold 1-periodic orbit and three-fold 1 -periodic orbit are also obtained. It is indicated that the number of periodic orbits bifurcated from this kind of homoclinic orbits depends heavily on the strength of the inclination flip.
文摘The homoclinic bifurcations in four dimensional vector fields are investigated by setting up a local coordinates near the homoclinic orbit. This homoclinic orbit is nonprincipal in the meanings that its positive semi-orbit takes orbit flip and its unstable foliation takes inclination flip. The existence, nonexistence, uniqueness and coexistence of the 1-homoclinic orbit and the 1-periodic orbit are studied. The existence of the twofold periodic orbit and three-fold periodic orbit are also obtained.
文摘The paper studies a codimension-4 resonant homoclinic bifurcation with one orbit flip and two inclination flips, where the resonance takes place in the tangent direction of homoclinic orbit.Local active coordinate system is introduced to construct the Poincar′e returning map, and also the associated successor functions. We prove the existence of the saddle-node bifurcation, the perioddoubling bifurcation and the homoclinic-doubling bifurcation, and also locate the corresponding 1-periodic orbit, 1-homoclinic orbit, double periodic orbits and some 2n-homoclinic orbits.
文摘Flipped is a book written by American author Wendelin Van Draanen. It is a novel about young teenagers and was adapted into the famous film of the same name in 2010. The thesis employs speech acts, as pioneered by John Austin and further developed by John Searle, to investigate the influence of dialogues on characterization and plot development in Flipped. By exploring the theory of speech acts presented in dialogues between characters, the author deciphers the underlying intentions embodied in the dialogues and demonstrates the importance of the use of speech acts in dialogues in revealing the characters, driving the development of the plot and expressing the theme of the text.
基金financial support of the National Natural Science Foundation of China(Grant No.11974255)。
文摘Active rods propelled along their long axis align their velocities and orientations simultaneously in collision.However,as the propulsion is perpendicular to the long axis,velocity alignment becomes dynamically difficult.Here,we show that ellipsoidal Quincke roller propelled along their short-axis(perpendicular to the long axis)can align their velocities by flipping and form flocking with nematic order.The flipping arises from the reversible transition between the static parallel spinless state and the spinning transversal state of ellipsoidal Quincke rollers.This is possible only near(above)the critical field where both the parallel spinless state and the spinning transversal spinning are metastable.The flipping-facilitated alignment offers an extra aligning mechanism for elongate active agents,and the resulting active liquid crystals serve a model system to explore the defect dynamics as the propulsion deviates from the local nematic orientation which has not been addressed yet.
基金Key Research and Development Program of Shaanxi Province,“Exploring the Changes and Mechanisms of Cerebral Microcirculation in Patients with Cerebral Small Vessel Disease and Mild Cognitive Impairment Based on OCTA Assessment”(Project No.:2023-YBSF-569)Shaanxi Provincial People’s Hospital Science and Technology Development Incubation Fund,“Early Identification of Cognitive Impairment in Cerebral Small Vessel Disease Based on Eye Tracking Technology”(Project No.:2023YJY-72)Key Research and Development Program of Shaanxi Province,“Study on the Correlation between Deep Medullary Veins and Cognitive Dysfunction in Cerebral Small Vessel Disease”(Project No.:2023-YBSF-033)。
文摘Objective:To explore the application effect of group cooperative learning combined with flipped classroom in standardized training of emergency surgery resident physicians.Methods:95 resident physicians undergoing emergency surgery standardized training in our hospital were randomly divided into an experimental group(46,group cooperative learning+flipped classroom)and a control group(49,traditional teaching).The training period was 2 months.Results:The graduation assessment scores of the experimental group were higher than those of the control group(P<0.05).The improvement in critical thinking ability and self-learning ability was better than that of the control group(P<0.05).The response rate of“yes”to all items of course teaching satisfaction was significantly higher than that of the control group(P<0.05).The satisfaction scores for training teachers were higher than those of the control group(P<0.05).Conclusion:The teaching model of group cooperative learning combined with flipped classroom,through reconstructing the learning process and activating interactive participation,can significantly improve the clinical operation and theoretical foundation of emergency surgery standardized training students.It also cultivates core professional qualities such as critical thinking,self-learning,and team collaboration,providing a feasible paradigm for integrated medical education in this discipline.
基金Project(U2341254)supported by Ye Qisun Science Foundation of National Natural Science Foundation of ChinaProject(52475406)supported by the National Nature Science Foundation of ChinaProject(2024CY2-GJHX-32)supported by the Key R&D Program of Shaanxi Province,China。
文摘Effect of flip chip bonding parameters on microstructure at the interconnect interface and shear properties of 64.8Sn35.2Pb microbumps were investigated in this work.Results show that the main intermetallic compound(IMC)at the interconnect interface is(Ni,Cu)_(3)Sn_(4)phase,and meanwhile a small amount of(Cu,Ni)_(6)Sn_(5)phase with a size of 50−100 nm is formed around(Ni,Cu)_(3)Sn_(4)phase.The orientation relationship of[-1-56](Ni,Cu)_(3)Sn_(4)//[152](Cu,Ni)_(6)Sn_(5)and(601)(Ni,Cu)_(3)Sn_(4)//(-201)(Cu,Ni)_(6)Sn_(5)is found between these two phases,and the atomic matching at the interface of the two phases is low.The highest shear force of 77.3 gf is achieved in the 64.8Sn35.2Pb microbump at the peak temperature of 250℃and parameter V1 because dense IMCs and no cracks form at the interconnect interface.Two typical fracture modes of microbumps are determined as solder fracture and mixed fracture.The high thermal stress presenting in the thick IMCs layer induces crack initiation,and cracks propagate along theα/βphase boundaries in the Sn-Pb solder under shear force,leading to a mixed fracture mode in the microbumps.
文摘Flip-chip technology is widely used in integrated circuit(IC)packaging.Molded underfill transfer molding is the most common process for these products,as the chip and solder bumps must be protected by the encapsulating material to ensure good reliability.Flow-front merging usually occurs during the molding process,and air is then trapped under the chip,which can form voids in the molded product.The void under the chip may cause stability and reliability problems.However,the flow process is unobservable during the transfer molding process.The engineer can only check for voids in the molded product after the process is complete.Previous studies have used fluid visualization experiments and developed computational fluid dynamics simulation tools to investigate this issue.However,a critical gap remains in establishing a comprehensive three-dimensional model that integrates two-phase flow,accurate venting settings,and fluid surface tension for molded underfill void evaluation—validated by experimental fluid visualization.This study aims to address this gap in the existing literature.In this study,a fluid visualization experiment was designed to simulate the transfer molding process,allowing for the observation of flow-front merging and void formation behaviors.For comparison,a three-dimensional mold flow analysis was also performed.It was found that the numerical simulation of the trapped air compression process under the chip was more accurate when considering the capillary force.The effect of design factors is evaluated in this paper.The results show that the most important factors for void size are fluid viscosity,the gap height under the chip,transfer time,contact angle between the fluid and the contact surfaces,and transfer pressure.Specifically,a smaller gap height beneath the chip aggravates void formation,while lower viscosity,extended transfer time,reduced contact angle,and increased transfer pressure are effective in minimizing void size.The overall results of this study will be useful for product and process design in selecting appropriate solutions for IC packaging,particularly in the development of void-free molded-underfill flip-chip packages.These findings support the optimization of industrial packaging processes in semiconductor manufacturing by guiding material selection and process parameters,ultimately enhancing package reliability and yield.
文摘Objective:To explore the application effect of an information-based flipped classroom teaching model in nursing education of rheumatology and immunology,providing empirical evidence for optimizing specialized nursing education models.Methods:Eighty nursing students from the 2021 grade of Xi’an Medical University were selected as research subjects and randomly divided into an experimental group(n=40)and a control group(n=40)using a random number table method.The control group received traditional lecture-based teaching,while the experimental group underwent information-based flipped classroom teaching.The theoretical knowledge scores and practical operation assessment scores of the two groups were compared after teaching,and the teaching satisfaction of the experimental group students was evaluated through a questionnaire survey.Results:The theoretical knowledge score(85.60±5.20)and practical operation score(88.30±4.70)of the experimental group were significantly higher than those of the control group(76.20±6.50)and(75.80±5.90),respectively.The differences were statistically significant(p<0.05).The satisfaction scores of all dimensions in the experimental group were significantly higher than those in the control group,and the differences were statistically significant(p<0.05).Conclusion:The information-based flipped classroom teaching model can effectively improve the quality of nursing teaching in rheumatology and immunology,enhance students’knowledge mastery and practical abilities,and is worthy of promotion and application in clinical nursing teaching.
基金This research received grant from 2022 Undergraduate Education and Teaching Research Project of Fujian Medical University(22028).
文摘Objective:This study aimed to investigate the learning expectations of undergraduate nursing students regarding the flipped Health Assessment course.Methods:This descriptive,qualitative study was conducted at a medical university in Fuzhou,Fujian Province,China.An interview outline was designed based on the core dimensions of Expectation Confirmation Theory(expectation sources,expectation content,and expectation importance).Thirty second-year undergraduate nursing students who had completed first-year basic medical courses and were about to take the flipped Health Assessment course were interviewed between June and July 2022.Interview data were analyzed using qualitative content analysis.Results:Five major themes and thirteen subthemes were identified.Theme 1 was expectation sourcesperceived learning difficulties from past experiences,which included four subthemes:insufficient autonomous learning ability,confusion regarding learning methods,insufficient engagement in learning,and low professional identity.Theme 2 included knowledge and information expectations,which comprised three subthemes:knowledge to improve professional competence,knowledge to enhance academic competitiveness,and knowledge to boost self-efficacy.Theme 3 comprised logical expectations and included two subthemes:flexible teaching methods and efficient instructional tools.Theme 4,pleasure expectations,included two subthemes:vivid teaching styles and diversified teaching evaluations.Theme 5 comprised professional value expectations and included two subthemes:teachers'responsible professional attitudes and gentle emotional support.Conclusion:Students'learning expectations originate from perceived learning difficulties,such as insufficient learning autonomy and engagement,confusion about learning methods,and a lack of professional identity.They showed various learning expectations for the flipped Health Assessment course,including knowledge and information,logic,pleasure,and professional value expectations.
