振动激发形核装置由激发形核棒、升降、测温、振动、冷却、减震等系统组成。在45 t Q345B钢扁锭浇铸过程,高度200mm振动激发形核棒置于铸锭中心处,插入钢液深度50~80mm。试验结果表明,(1)在模铸过程使用振动激发形核装置安全可靠;(2)冷...振动激发形核装置由激发形核棒、升降、测温、振动、冷却、减震等系统组成。在45 t Q345B钢扁锭浇铸过程,高度200mm振动激发形核棒置于铸锭中心处,插入钢液深度50~80mm。试验结果表明,(1)在模铸过程使用振动激发形核装置安全可靠;(2)冷却气体达到40 m^3/h棒体表面有结壳现象,而当冷却气体液量在20 m^3/h,棒体表面很光滑,合适的冷却气体流量为20~40 m^3/h,激发形核棒表面和钢液间的温差为55~80 C;(3)通过探伤检测,振动处理板Ⅱ级合格,而未经振动处理的常规板有连续性缺陷,判定为不合格。展开更多
For understanding the rock microscopic damage and dynamic mechanical properties subjected to recurrent freeze-thaw cycles, experiments for five groups of homogeneous sandstone under different freeze-thaw cycles were c...For understanding the rock microscopic damage and dynamic mechanical properties subjected to recurrent freeze-thaw cycles, experiments for five groups of homogeneous sandstone under different freeze-thaw cycles were conducted. After freezethaw, nuclear magnetic resonance(NMR) tests and impact loading tests were carried out, from which microscopic damage characteristics of sandstone and dynamic mechanical parameters were obtained. The results indicate that the porosity increases with the increase of cycle number, the rate of porosity growth descends at the beginning of freeze-thaw, yet accelerates after a certain number of cycles. The proportion of pores with different sizes changes dynamically and the multi-scale distribution of pores tends to develop on pore structure with the continuing impact of freeze-thaw and thawing. Dynamic compressive stress-strain curve of sandstone undergoing freeze-thaw can be divided into four phases, and the phase of compaction is inconspicuous compared with the static curve. Elastic modulus and dynamic peak intensity of sandstone gradually decrease with freeze-thaw cycles, while peak strain increases. The higher the porosity is, the more serious the degradation of dynamic intensity is. The porosity is of a polynomial relationship with the dynamic peak intensity.展开更多
Dynamic casual modeling of functional magnetic resonance imaging（fMRI） signals is employed to explore critical emotional neurocircuitry under sad stimuli. The intrinsic model of emotional loops is built on the basis...Dynamic casual modeling of functional magnetic resonance imaging（fMRI） signals is employed to explore critical emotional neurocircuitry under sad stimuli. The intrinsic model of emotional loops is built on the basis of Papez＇s circuit and related prior knowledge, and then three modulatory connection models are established. In these models, stimuli are placed at different points, which represents they affect the neural activities between brain regions, and these activities are modulated in different ways. Then, the optimal model is selected by Bayesian model comparison. From group analysis, patients＇ intrinsic and modulatory connections from the anterior cingulate cortex （ACC） to the right inferior frontal gyrus （rlFG） are significantly higher than those of the control group. Then the functional connection parameters of the model are selected as classifier features. The classification accuracy rate from the support vector machine（SVM） classifier is 80.73%, which, to some extent, validates the effectiveness of the regional connectivity parameters for depression recognition and provides a new approach for the clinical diagnosis of depression.展开更多
The dynamic mechanical properties of basalt affected by microwave were investigated by performing dynamic compressive tests using the SHPB system.Meanwhile,the thermal damage of the treated basalt was characterized by...The dynamic mechanical properties of basalt affected by microwave were investigated by performing dynamic compressive tests using the SHPB system.Meanwhile,the thermal damage of the treated basalt was characterized by ultrasonic non-destructive testing and nuclear magnetic resonance technology.The results show that with the increase of microwave power and exposure time,the P-wave velocity,dynamic compressive strength and elastic modulus decrease continuously,and the dynamic failure mode tends to be a more complex fracturing.The increase in microwave power and exposure time can enhance the temperature difference and transfer coefficient among minerals,hence intensifying the rock damage induced by thermal shock.展开更多
fMRI （Functional Magnetic Resonance Imaging） is a relatively new technique that uses MRI （Magnetic Resonance Imaging） to measure the hemodynamic response （change in blood flow） related to neural activity in the ...fMRI （Functional Magnetic Resonance Imaging） is a relatively new technique that uses MRI （Magnetic Resonance Imaging） to measure the hemodynamic response （change in blood flow） related to neural activity in the brain. This paper aims to explore and identify the obstacles facing the implementation and applications of IMRI in radiology departments within Jeddah city by analyzing related data received by direct questionnaires and interviews with all the people working in MRI units in Jeddah city and finds that the major obstacle is lacking of awareness of fMRI among medical professionals and their training.展开更多
Breath-hold clue MRI was employed for the identification of severe coronary artery stenoses after 0. 56 mg/kg of dipyridamole was infused. Fourteen patients without myocardial infarction but with ≥70% di- ameter narr...Breath-hold clue MRI was employed for the identification of severe coronary artery stenoses after 0. 56 mg/kg of dipyridamole was infused. Fourteen patients without myocardial infarction but with ≥70% di- ameter narrowing of 1 or 2 major coronary arteries were studied. Each patient underwent coronary angiog- raphy, MRI at rest and during stress. Segmental wall motion abnormalities were visually assessed in a clue loop, followed by quantitative analysis by calculation of percent systolic wall thickening(%SWth). The re- suits showed that the sensitivities of 70% and 90% were present for the qualitative and quantitative analy- ses, respectively, in respect to the approximate specificities(82 % & 86% ). Further quantitative analysis showed that sensitivities and specificities were 88% and 88% for l-vessel disease versus 92% and 83% for 2-vessel disease; 86 % and 100% for LAD, 100% and 70% for LCX, 89% and 100% for RCA. We con- cluded that quantitative analysis is significantly superior to qualitative analysis for the identification of se- vere coronary stenosis while d ipyridamole- induced wall motion abnormalities were assessed by breath - hold cine MRI.展开更多
The scaling behaviors of the nucleon resonance transition amplitudes from perturbative QCD (PQCD) are utilized to parametrize the amplitudes of the first negative-parity nucleon resonance . Our analysis indicates that...The scaling behaviors of the nucleon resonance transition amplitudes from perturbative QCD (PQCD) are utilized to parametrize the amplitudes of the first negative-parity nucleon resonance . Our analysis indicates that the constraints of the transition amplitude for the resonance at the limit by QCD sum rule calculations are not applicable at a moderate range of compared with the present available data if the contribution of is dominant in the limit.展开更多
基金Project(2013YQ17046310)supported by the National Key Scientific Instrument and Equipment Development Project of ChinaProject(2013M542138)supported by China Postdoctoral Science FoundationProjects(20130162110010,20130162120012)supported by Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘For understanding the rock microscopic damage and dynamic mechanical properties subjected to recurrent freeze-thaw cycles, experiments for five groups of homogeneous sandstone under different freeze-thaw cycles were conducted. After freezethaw, nuclear magnetic resonance(NMR) tests and impact loading tests were carried out, from which microscopic damage characteristics of sandstone and dynamic mechanical parameters were obtained. The results indicate that the porosity increases with the increase of cycle number, the rate of porosity growth descends at the beginning of freeze-thaw, yet accelerates after a certain number of cycles. The proportion of pores with different sizes changes dynamically and the multi-scale distribution of pores tends to develop on pore structure with the continuing impact of freeze-thaw and thawing. Dynamic compressive stress-strain curve of sandstone undergoing freeze-thaw can be divided into four phases, and the phase of compaction is inconspicuous compared with the static curve. Elastic modulus and dynamic peak intensity of sandstone gradually decrease with freeze-thaw cycles, while peak strain increases. The higher the porosity is, the more serious the degradation of dynamic intensity is. The porosity is of a polynomial relationship with the dynamic peak intensity.
基金The National Natural Science Foundation of China(No.30900356,81071135)
文摘Dynamic casual modeling of functional magnetic resonance imaging（fMRI） signals is employed to explore critical emotional neurocircuitry under sad stimuli. The intrinsic model of emotional loops is built on the basis of Papez＇s circuit and related prior knowledge, and then three modulatory connection models are established. In these models, stimuli are placed at different points, which represents they affect the neural activities between brain regions, and these activities are modulated in different ways. Then, the optimal model is selected by Bayesian model comparison. From group analysis, patients＇ intrinsic and modulatory connections from the anterior cingulate cortex （ACC） to the right inferior frontal gyrus （rlFG） are significantly higher than those of the control group. Then the functional connection parameters of the model are selected as classifier features. The classification accuracy rate from the support vector machine（SVM） classifier is 80.73%, which, to some extent, validates the effectiveness of the regional connectivity parameters for depression recognition and provides a new approach for the clinical diagnosis of depression.
基金supported by the National Natural Science Foundation of China(Nos.51774325,41972283,11972378).
文摘The dynamic mechanical properties of basalt affected by microwave were investigated by performing dynamic compressive tests using the SHPB system.Meanwhile,the thermal damage of the treated basalt was characterized by ultrasonic non-destructive testing and nuclear magnetic resonance technology.The results show that with the increase of microwave power and exposure time,the P-wave velocity,dynamic compressive strength and elastic modulus decrease continuously,and the dynamic failure mode tends to be a more complex fracturing.The increase in microwave power and exposure time can enhance the temperature difference and transfer coefficient among minerals,hence intensifying the rock damage induced by thermal shock.
文摘fMRI （Functional Magnetic Resonance Imaging） is a relatively new technique that uses MRI （Magnetic Resonance Imaging） to measure the hemodynamic response （change in blood flow） related to neural activity in the brain. This paper aims to explore and identify the obstacles facing the implementation and applications of IMRI in radiology departments within Jeddah city by analyzing related data received by direct questionnaires and interviews with all the people working in MRI units in Jeddah city and finds that the major obstacle is lacking of awareness of fMRI among medical professionals and their training.
基金Fondation de FranceHospices Civils de Lyon!(Recherche Clinique Contrat 1994)
文摘Breath-hold clue MRI was employed for the identification of severe coronary artery stenoses after 0. 56 mg/kg of dipyridamole was infused. Fourteen patients without myocardial infarction but with ≥70% di- ameter narrowing of 1 or 2 major coronary arteries were studied. Each patient underwent coronary angiog- raphy, MRI at rest and during stress. Segmental wall motion abnormalities were visually assessed in a clue loop, followed by quantitative analysis by calculation of percent systolic wall thickening(%SWth). The re- suits showed that the sensitivities of 70% and 90% were present for the qualitative and quantitative analy- ses, respectively, in respect to the approximate specificities(82 % & 86% ). Further quantitative analysis showed that sensitivities and specificities were 88% and 88% for l-vessel disease versus 92% and 83% for 2-vessel disease; 86 % and 100% for LAD, 100% and 70% for LCX, 89% and 100% for RCA. We con- cluded that quantitative analysis is significantly superior to qualitative analysis for the identification of se- vere coronary stenosis while d ipyridamole- induced wall motion abnormalities were assessed by breath - hold cine MRI.
文摘The scaling behaviors of the nucleon resonance transition amplitudes from perturbative QCD (PQCD) are utilized to parametrize the amplitudes of the first negative-parity nucleon resonance . Our analysis indicates that the constraints of the transition amplitude for the resonance at the limit by QCD sum rule calculations are not applicable at a moderate range of compared with the present available data if the contribution of is dominant in the limit.
