HANBIT is a magnetic mirror confinement device. Recent physics experimentshave been mainly focused on identifying discharge characteristics and on getting stable plasmaproduction and operation modes, by using a 500 kW...HANBIT is a magnetic mirror confinement device. Recent physics experimentshave been mainly focused on identifying discharge characteristics and on getting stable plasmaproduction and operation modes, by using a 500 kW slot antenna system at a fixed RF frequency of 3.5MHz and varying discharge conditions such as fueling rate, RF power, and B-field intensity incentral cell. Two distinct operation modes are found to be very sensitive to the RF power as well asthe ratio of the RF frequency to the ion cyclotron frequency. A MHD interchange mode of m = - 1 isclearly observed and the stabilizing mechanism can be explained by the sideband coupling theory.展开更多
For the success of PAL-XFEL, two critical systems, namely a low emittance injector and a variable gap out-vacuum undulator, are under development. In order to realize the target emittance of the PAL-XFEL injector we c...For the success of PAL-XFEL, two critical systems, namely a low emittance injector and a variable gap out-vacuum undulator, are under development. In order to realize the target emittance of the PAL-XFEL injector we carried out an optimization study of various parameters, such as the laser beam transverse profile, the laser pulse length, the laser phase,and the gun energy. The transverse emittance measured at the Injector Test Facility(ITF) is εx=0.48±0.01 mm mrad.An undulator prototype based on the EU-XFEL design and modified for PAL-XFEL was built and tested. A local-K pole tuning procedure was developed and tested. A significant reduction(90%) of the local-K fluctuation was observed. The requirement of undulator field reproducibility better than 2×10-4and the undulator gap setting accuracy below 1 μm were achieved for the prototype. The optical phase jitter after the pole height tuning at the tuning gap was calculated to be 2.6? rms, which satisfies the requirement of 5.0?.展开更多
Reproducibility of clinical output is important when investigating therapeutic efficacy in pre-clinical animal studies.Due to its physiological relevance,a swine myocardial infarction(MI)model has been widely used to ...Reproducibility of clinical output is important when investigating therapeutic efficacy in pre-clinical animal studies.Due to its physiological relevance,a swine myocardial infarction(MI)model has been widely used to evaluate the effectiveness of stem cells or tissue-engineered constructs for ischemic heart diseases.Several methods are used to induce MI in the swine model.However,it is difficult,using these approaches,to obtain a similar level of functional outcomes from a group of animals due to interpersonal variation,leading to increased experimental cost.Hence,in order to minimize human intervention,we developed an approach to use a customized occluder that has dimensional similarities with that of the coronary artery of animals in the case of the swine model.We carried out angiography to measure the diameter of the middle left anterior descending artery of each individual animal to fabricate the customized occluder using a 3D-printing system.The fabricated occluder contained a central hole smaller than that of the targeted middle left anterior descending artery to mimic an atherosclerotic coronary artery that has an approximately 20%blocked condition.Interestingly,the 3D-printed occluder can provide continuous blood flow through the central pore,indicating a high survival rate(88%)of up to 28 days post-operation.This method showed the possibility of creating consistent myocardial infarction induction as compared to the conventional representative closed-chest method(50%survival rate),thus highlighting how our method can have a profound effect on accelerating reliable experiments for developing new therapeutic approaches to ischemic heart diseases.展开更多
This study was carried out to observe the effects of sodium fluoride on acetylcholinesterase (AChE) activities in the cerebral synaptic membranes (SPM) and the peripheral red blood cells (RBC) of rats by in vivo and i...This study was carried out to observe the effects of sodium fluoride on acetylcholinesterase (AChE) activities in the cerebral synaptic membranes (SPM) and the peripheral red blood cells (RBC) of rats by in vivo and in vitro experiments. In the in vivo study,pregnant rats ingested ad libitum fluorinated drinking water (5, 15, 50 ppm F ) during their gestation and lactation. It was shown that the AChE activities of the SPM and peripheral RBCs in maternal rats exposed 5 ~ 50 ppm F for 60 days were elevated significantly by 30. 0 ~ 67. 6 % and 12. 5 ~ 31. 9 % in a dose-dependent manner, respectively. The AChE activities of their offspring 80 days after birth were also increaased (8. 7 ~ 28. 7 % for SPM and20. 6 ~ 32. 4 % for RBC). In contrast, the AChE activities of SPM in vitro were inhibited by 5. 0~ 50 .0 mmol F /L treatment in a time-and dose dependent manner. Analaysis with the Hanes plots suggested that the enzymesubstrate kinetics are consistent with a mixed type ofinhibition.展开更多
The impact problem of a flexible multibody system is a non-smooth, high-transient, and strong-nonlinear dynamic process with variable boundary. How to model the contact/impact process accurately and efficiently is one...The impact problem of a flexible multibody system is a non-smooth, high-transient, and strong-nonlinear dynamic process with variable boundary. How to model the contact/impact process accurately and efficiently is one of the main difficulties in many engineering applications. The numerical approaches being used widely in impact analysis are mainly from two fields： multibody system dynamics （MBS） and computational solid mechanics （CSM）. Approaches based on MBS provide a more efficient yet less accurate analysis of the contact/impact problems, while approaches based on CSM are well suited for particularly high accuracy needs, yet require very high computational effort. To bridge the gap between accuracy and efficiency in the dynamic simulation of a flexible multibody system with contacts/impacts, a partition method is presented considering that the contact body is divided into two parts, an impact region and a non-impact region. The impact region is modeled using the finite element method to guarantee the local accuracy, while the non-impact region is modeled using the modal reduction approach to raise the global efficiency. A three-dimensional rod-plate impact experiment is designed and performed to validate the numerical results. The principle for how to partition the contact bodies is proposed： the maximum radius of the impact region can be estimated by an analytical method, and the modal truncation orders of the non-impact region can be estimated by the highest frequency of the signal measured. The simulation results using the presented method are in good agreement with the experimental results. It shows that this method is an effec-rive formulation considering both accuracy and efficiency. Moreover, a more complicated multibody impact problem of a crank slider mechanism is investigated to strengthen this conclusion.展开更多
A flexible beam with large overall rotating motion impacting with a rigid slope is studied in this paper. The tangential friction force caused by the oblique impact is analyzed. The tangential motion of the system is ...A flexible beam with large overall rotating motion impacting with a rigid slope is studied in this paper. The tangential friction force caused by the oblique impact is analyzed. The tangential motion of the system is divided into a stick state and a slip state. The contact constraint model and Coulomb friction model are used respectively to deal with the two states. Based on this hybrid modeling method, dynamic equations of the system, which include all states（before, during, and after the collision）are obtained. Simulation results of a concrete example are compared with the results obtained from two other models： a nontangential friction model and a modified Coulomb model. Differences in the results from the three models are discussed. The tangential friction force cannot be ignored when an oblique impact occurs. In addition, the results obtained from the model proposed in this paper are more consistent with real movement.展开更多
基金The project supported by the Korea Ministry of Science and Technology
文摘HANBIT is a magnetic mirror confinement device. Recent physics experimentshave been mainly focused on identifying discharge characteristics and on getting stable plasmaproduction and operation modes, by using a 500 kW slot antenna system at a fixed RF frequency of 3.5MHz and varying discharge conditions such as fueling rate, RF power, and B-field intensity incentral cell. Two distinct operation modes are found to be very sensitive to the RF power as well asthe ratio of the RF frequency to the ion cyclotron frequency. A MHD interchange mode of m = - 1 isclearly observed and the stabilizing mechanism can be explained by the sideband coupling theory.
基金supported by the Ministry of Science,ICT and Future Planning of Korea
文摘For the success of PAL-XFEL, two critical systems, namely a low emittance injector and a variable gap out-vacuum undulator, are under development. In order to realize the target emittance of the PAL-XFEL injector we carried out an optimization study of various parameters, such as the laser beam transverse profile, the laser pulse length, the laser phase,and the gun energy. The transverse emittance measured at the Injector Test Facility(ITF) is εx=0.48±0.01 mm mrad.An undulator prototype based on the EU-XFEL design and modified for PAL-XFEL was built and tested. A local-K pole tuning procedure was developed and tested. A significant reduction(90%) of the local-K fluctuation was observed. The requirement of undulator field reproducibility better than 2×10-4and the undulator gap setting accuracy below 1 μm were achieved for the prototype. The optical phase jitter after the pole height tuning at the tuning gap was calculated to be 2.6? rms, which satisfies the requirement of 5.0?.
基金supported by the Bio&Medical Technology Development Program and Basic Science Research Program through the National Research Foundation(NRF),funded by the Korean government(MSIT)(No.2018M3A9E2024584)the Ministry of Trade,Industry and Energy(MOTIE)and Korea Institute for Advancement of Technology(KIAT)through the International Cooperative R&D program(No.P0011282).
文摘Reproducibility of clinical output is important when investigating therapeutic efficacy in pre-clinical animal studies.Due to its physiological relevance,a swine myocardial infarction(MI)model has been widely used to evaluate the effectiveness of stem cells or tissue-engineered constructs for ischemic heart diseases.Several methods are used to induce MI in the swine model.However,it is difficult,using these approaches,to obtain a similar level of functional outcomes from a group of animals due to interpersonal variation,leading to increased experimental cost.Hence,in order to minimize human intervention,we developed an approach to use a customized occluder that has dimensional similarities with that of the coronary artery of animals in the case of the swine model.We carried out angiography to measure the diameter of the middle left anterior descending artery of each individual animal to fabricate the customized occluder using a 3D-printing system.The fabricated occluder contained a central hole smaller than that of the targeted middle left anterior descending artery to mimic an atherosclerotic coronary artery that has an approximately 20%blocked condition.Interestingly,the 3D-printed occluder can provide continuous blood flow through the central pore,indicating a high survival rate(88%)of up to 28 days post-operation.This method showed the possibility of creating consistent myocardial infarction induction as compared to the conventional representative closed-chest method(50%survival rate),thus highlighting how our method can have a profound effect on accelerating reliable experiments for developing new therapeutic approaches to ischemic heart diseases.
文摘This study was carried out to observe the effects of sodium fluoride on acetylcholinesterase (AChE) activities in the cerebral synaptic membranes (SPM) and the peripheral red blood cells (RBC) of rats by in vivo and in vitro experiments. In the in vivo study,pregnant rats ingested ad libitum fluorinated drinking water (5, 15, 50 ppm F ) during their gestation and lactation. It was shown that the AChE activities of the SPM and peripheral RBCs in maternal rats exposed 5 ~ 50 ppm F for 60 days were elevated significantly by 30. 0 ~ 67. 6 % and 12. 5 ~ 31. 9 % in a dose-dependent manner, respectively. The AChE activities of their offspring 80 days after birth were also increaased (8. 7 ~ 28. 7 % for SPM and20. 6 ~ 32. 4 % for RBC). In contrast, the AChE activities of SPM in vitro were inhibited by 5. 0~ 50 .0 mmol F /L treatment in a time-and dose dependent manner. Analaysis with the Hanes plots suggested that the enzymesubstrate kinetics are consistent with a mixed type ofinhibition.
基金supported by the National Natural Science Foundation of China (Grants 11772188, 11132007)
文摘The impact problem of a flexible multibody system is a non-smooth, high-transient, and strong-nonlinear dynamic process with variable boundary. How to model the contact/impact process accurately and efficiently is one of the main difficulties in many engineering applications. The numerical approaches being used widely in impact analysis are mainly from two fields： multibody system dynamics （MBS） and computational solid mechanics （CSM）. Approaches based on MBS provide a more efficient yet less accurate analysis of the contact/impact problems, while approaches based on CSM are well suited for particularly high accuracy needs, yet require very high computational effort. To bridge the gap between accuracy and efficiency in the dynamic simulation of a flexible multibody system with contacts/impacts, a partition method is presented considering that the contact body is divided into two parts, an impact region and a non-impact region. The impact region is modeled using the finite element method to guarantee the local accuracy, while the non-impact region is modeled using the modal reduction approach to raise the global efficiency. A three-dimensional rod-plate impact experiment is designed and performed to validate the numerical results. The principle for how to partition the contact bodies is proposed： the maximum radius of the impact region can be estimated by an analytical method, and the modal truncation orders of the non-impact region can be estimated by the highest frequency of the signal measured. The simulation results using the presented method are in good agreement with the experimental results. It shows that this method is an effec-rive formulation considering both accuracy and efficiency. Moreover, a more complicated multibody impact problem of a crank slider mechanism is investigated to strengthen this conclusion.
基金supported by the National Natural Science Foundation of China(Grants 11272155,11132007,and11502113)the 333 Project of Jiangsu Province in China(Grant BRA2011172)the Fundamental Research Funds for Central Universities(Grant 30920130112009)
文摘A flexible beam with large overall rotating motion impacting with a rigid slope is studied in this paper. The tangential friction force caused by the oblique impact is analyzed. The tangential motion of the system is divided into a stick state and a slip state. The contact constraint model and Coulomb friction model are used respectively to deal with the two states. Based on this hybrid modeling method, dynamic equations of the system, which include all states（before, during, and after the collision）are obtained. Simulation results of a concrete example are compared with the results obtained from two other models： a nontangential friction model and a modified Coulomb model. Differences in the results from the three models are discussed. The tangential friction force cannot be ignored when an oblique impact occurs. In addition, the results obtained from the model proposed in this paper are more consistent with real movement.
