The microstructure and conductive mechanism of high density polyethylene/carbon black (HDPE/CB) composite were investigated by positron annihilation lifetime spectroscopy (PALS). The PALS were measured in two series o...The microstructure and conductive mechanism of high density polyethylene/carbon black (HDPE/CB) composite were investigated by positron annihilation lifetime spectroscopy (PALS). The PALS were measured in two series of samples, one with various CB contents in the composites and the other with various gamma-irradiation doses in HDPE/CB composite containing 20 wt% CB. It was found that CB particles distribute in the amorphous regions, the CB critical content value in HDPE/CB composite is about 16.7 wt% and the suitable gamma-irradiation dose for improving the conductive behavior of HDPE/CB composite is about 20 Mrad. The result observed for the second set of samples suggests that gamma-irradiation causes not only cross-linking in amorphous regions but also destruction of the partial crystalline structure. Therefore, a suitable irradiation dose, about 20 Mrad, can induce sufficient cross-linking in the amorphous regions without enhancing the decomposition of crystalline structure, so that the positive temperature coefficient (PTC) effect remains while the negative temperature coefficient (NTC) effect is suppressed. A new interpretation of the conductive mechanism, which might provide a more detailed explanation of the PTC effect and the NTC effect has been proposed.展开更多
Since 1992,task groups have used free nerve auto grafts to bridge partially transected nerves from the dominant area of the normal cerebral cortex to nerves that innervate spastic muscles from a diseased cerebral cort...Since 1992,task groups have used free nerve auto grafts to bridge partially transected nerves from the dominant area of the normal cerebral cortex to nerves that innervate spastic muscles from a diseased cerebral cortex,using transplanting sutures to alleviate the muscle spasm of cerebral palsy caused by different diseases. This has facilitated rebuilding of some of its neurological function. In this study,80 such patients were followed up,including 20 patients with traumatic brain injury,32 patients with stroke,and 28 pediatric patients with cerebral palsy. After postoperative follow-up of 3 to 21 years,the efficacy rate of this operation was 100% and the excellent and good spasm relief rate was 82.5%.展开更多
A LaBr3：Ce scintillator has a high light output （～60000 p.e/MeV） and a short decay constant （25 ns）, which makes it good for time spectrometry. Compared with a BaF2 scintillator, it can bear a much higher count ...A LaBr3：Ce scintillator has a high light output （～60000 p.e/MeV） and a short decay constant （25 ns）, which makes it good for time spectrometry. Compared with a BaF2 scintillator, it can bear a much higher count rate, and can be coupled to photomultipliers without using a quartz window. In this work, a positron annihilation lifetime spectrometer （PALS） consisting of two bulks of φ25 mm×25 mm LaBr3：Ce scin- tillator coupled to two XP20D0 photomultipliers, respectively, was built. A time resolution of FWHM=206 ps was measured for the PALS with a 60Co source at the energy window for 22Na. With this spectrometer, a reasonable lifetime value τ =221±4 ps in a pure Si sample is obtained, which means that the utilization of LaBr3：Ce as the detector for a PALS is feasible.展开更多
This study investigated the instructional preferences of full time adult credential students after they took a live course called Principles of Adult Education at California State University, Long Beach (CSULB) in the...This study investigated the instructional preferences of full time adult credential students after they took a live course called Principles of Adult Education at California State University, Long Beach (CSULB) in the fall semester of 2002. These full time adult credential students had been working on their adult teaching credentials to meet the competencies specified by the California Commission on Teacher Credentialing. The course introduced students to Andragogy developed by Malcolm Knowles out of the andragogical model developed by Lindeman (1926). The study used Principles of Adult Learning Scales (PALS), advanced by Gary Conti in 1983 to measure instructional preferences. Data were collected from 30 (100% of 30) full time adult credential students enrolled in a live course to determine their instructional preferences of helping adults learn. The results of the study showed in most cases these adult learning professionals taught adult students andragogically; in some cases they taught adult students pedagogically.展开更多
SrTi1-xFexO3-δ ceramics were prepared using a traditional solid-state reaction method. From X-ray diffraction(XRD) result, we found that the doped Fe^3+ dissolved in the lattice, and no secondary phase was observed. ...SrTi1-xFexO3-δ ceramics were prepared using a traditional solid-state reaction method. From X-ray diffraction(XRD) result, we found that the doped Fe^3+ dissolved in the lattice, and no secondary phase was observed. Cation vacancies in perovskite oxides were identified via positron annihilation lifetime spectroscopy(PALS) measurements. Undoped and Fe-doped SrTiO3 ceramics and single-crystal SrTiO3 were measured by PALS at room temperature. The results show that the main defects in undoped SrTiO3 ceramics are Ti-related defects, and the isolated Ti vacancy lifetime is about 183.4 ps. With the increase of Fe^3+, the concentration of the Ti vacancies decreases accompanied by the appearance of the V^nSr-nV^**O(defect association of Sr vacancies and multiple O vacancies) vacancy defect complexes.展开更多
The characterization of sulfonated polyetherketone (SPEK-C) films was investigated by using positronannihilation lifetime spectroscopy (PALS) and atomic force microscopy (AFM). It was found that free volume radiusand ...The characterization of sulfonated polyetherketone (SPEK-C) films was investigated by using positronannihilation lifetime spectroscopy (PALS) and atomic force microscopy (AFM). It was found that free volume radiusand intensity depend on the variation of sulfonation degree and solvent evaporation time of the films. Pore size anddistribution determined from PALS and AFM measurements showed reasonable agreement.展开更多
基金This work was supported by the National Natural Science Foundation of China (Grant No: 19875050, 10075041, 10075044).
文摘The microstructure and conductive mechanism of high density polyethylene/carbon black (HDPE/CB) composite were investigated by positron annihilation lifetime spectroscopy (PALS). The PALS were measured in two series of samples, one with various CB contents in the composites and the other with various gamma-irradiation doses in HDPE/CB composite containing 20 wt% CB. It was found that CB particles distribute in the amorphous regions, the CB critical content value in HDPE/CB composite is about 16.7 wt% and the suitable gamma-irradiation dose for improving the conductive behavior of HDPE/CB composite is about 20 Mrad. The result observed for the second set of samples suggests that gamma-irradiation causes not only cross-linking in amorphous regions but also destruction of the partial crystalline structure. Therefore, a suitable irradiation dose, about 20 Mrad, can induce sufficient cross-linking in the amorphous regions without enhancing the decomposition of crystalline structure, so that the positive temperature coefficient (PTC) effect remains while the negative temperature coefficient (NTC) effect is suppressed. A new interpretation of the conductive mechanism, which might provide a more detailed explanation of the PTC effect and the NTC effect has been proposed.
基金supported by the Shanghai Science and Technology Project(No.10411953800)
文摘Since 1992,task groups have used free nerve auto grafts to bridge partially transected nerves from the dominant area of the normal cerebral cortex to nerves that innervate spastic muscles from a diseased cerebral cortex,using transplanting sutures to alleviate the muscle spasm of cerebral palsy caused by different diseases. This has facilitated rebuilding of some of its neurological function. In this study,80 such patients were followed up,including 20 patients with traumatic brain injury,32 patients with stroke,and 28 pediatric patients with cerebral palsy. After postoperative follow-up of 3 to 21 years,the efficacy rate of this operation was 100% and the excellent and good spasm relief rate was 82.5%.
基金Supported by National Natural Science Foundation of China(10805049,10775149)
文摘A LaBr3：Ce scintillator has a high light output （～60000 p.e/MeV） and a short decay constant （25 ns）, which makes it good for time spectrometry. Compared with a BaF2 scintillator, it can bear a much higher count rate, and can be coupled to photomultipliers without using a quartz window. In this work, a positron annihilation lifetime spectrometer （PALS） consisting of two bulks of φ25 mm×25 mm LaBr3：Ce scin- tillator coupled to two XP20D0 photomultipliers, respectively, was built. A time resolution of FWHM=206 ps was measured for the PALS with a 60Co source at the energy window for 22Na. With this spectrometer, a reasonable lifetime value τ =221±4 ps in a pure Si sample is obtained, which means that the utilization of LaBr3：Ce as the detector for a PALS is feasible.
文摘This study investigated the instructional preferences of full time adult credential students after they took a live course called Principles of Adult Education at California State University, Long Beach (CSULB) in the fall semester of 2002. These full time adult credential students had been working on their adult teaching credentials to meet the competencies specified by the California Commission on Teacher Credentialing. The course introduced students to Andragogy developed by Malcolm Knowles out of the andragogical model developed by Lindeman (1926). The study used Principles of Adult Learning Scales (PALS), advanced by Gary Conti in 1983 to measure instructional preferences. Data were collected from 30 (100% of 30) full time adult credential students enrolled in a live course to determine their instructional preferences of helping adults learn. The results of the study showed in most cases these adult learning professionals taught adult students andragogically; in some cases they taught adult students pedagogically.
基金Supported by the National Natural Science Foundation of China(11575129,11275142)
文摘SrTi1-xFexO3-δ ceramics were prepared using a traditional solid-state reaction method. From X-ray diffraction(XRD) result, we found that the doped Fe^3+ dissolved in the lattice, and no secondary phase was observed. Cation vacancies in perovskite oxides were identified via positron annihilation lifetime spectroscopy(PALS) measurements. Undoped and Fe-doped SrTiO3 ceramics and single-crystal SrTiO3 were measured by PALS at room temperature. The results show that the main defects in undoped SrTiO3 ceramics are Ti-related defects, and the isolated Ti vacancy lifetime is about 183.4 ps. With the increase of Fe^3+, the concentration of the Ti vacancies decreases accompanied by the appearance of the V^nSr-nV^**O(defect association of Sr vacancies and multiple O vacancies) vacancy defect complexes.
文摘The characterization of sulfonated polyetherketone (SPEK-C) films was investigated by using positronannihilation lifetime spectroscopy (PALS) and atomic force microscopy (AFM). It was found that free volume radiusand intensity depend on the variation of sulfonation degree and solvent evaporation time of the films. Pore size anddistribution determined from PALS and AFM measurements showed reasonable agreement.
