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Aging effects of regional activation in a spatial task A functional magnetic resonance imaging study 被引量:1
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作者 Jong-Rak Park Dae-Woon Lim +6 位作者 Mi-Hyun Choi Su-Jeong Lee Jin-Seung Choi Hyung-Sik Kim Jeong-Han Yi Gye-Rae Tack Soon-Cheol Chung 《Neural Regeneration Research》 SCIE CAS CSCD 2009年第9期663-667,共5页
BACKGROUND: An increasing number of studies have shown the effects of aging in basic cognitive processing and higher cognitive functions using functional magnetic resonance imaging (fMRI). However, little is known ... BACKGROUND: An increasing number of studies have shown the effects of aging in basic cognitive processing and higher cognitive functions using functional magnetic resonance imaging (fMRI). However, little is known about the aging effects in diverse cognitive abilities, such as spatial learning and reasoning. OBJECTIVE: To investigate the effect of aging on spatial cognitive performance and regional brain activation based on fMRI. DESIGN, TIME, AND SETTING: A block design for fMRI observation. This study was performed at the fMRI Laboratory, Brain Science Research Center, Korea Advanced Institute of Science and Technology from March 2006 to May 2009. PARTICIPANTS: Eight right-handed, male, college students in their 20s (mean age 21.5 years) and six right-handed, male, adults in their 40s (mean age 45.7 years), who graduated from college, participated in the study. All subjects were healthy and had no prior history of psychiatric or neurological disorders. METHODS: A spatial task was presented while brain images were acquired using a 3T fMRI system (ISOL Technology, Korea). The spatial tasks involved selecting a shape that corresponded to a given figure using four examples, as well as selecting a development figure of a diagram. MAIN OUTCOME MEASURES: The accuracy rate (number of correct answers/total number of items x 100%) of spatial tasks was calculated. Using the subtraction procedure, the activated areas in the brain during spatial tasks were color-coded by T-score. The double subtraction method was used to analyze the effect of aging between the two age groups (20s versus 40s). RESULTS: The cerebellum, occipital lobe, parietal lobe, and frontal lobe were similarly activated in the two age groups. Increased brain activations, however, were observed in bilateral parietal and superior frontal lobes of the younger group. More activation was observed in bilateral middle frontal and right inferior frontal lobes in the older group. Compared with the older group, the younger men exhibited greater spatial performance (P = 0.012). CONCLUSION: Reduced cognitive function correlated with decreased activation areas in the parietal lobe and altered activation in the frontal lobe. 展开更多
关键词 functional magnetic resonance imaging AGING regional activation spatial task
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Acupuncture inhibits cue-induced heroin craving and brain activation 被引量:5
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作者 Xinghui Cai Xiaoge Song +3 位作者 Chuanfu Li Chunsheng Xu Xiliang Li Qi Lu 《Neural Regeneration Research》 SCIE CAS CSCD 2012年第33期2607-2616,共10页
Previous research using functional MRI has shown that specific brain regions associated with drug dependence and cue-elicited heroin craving are activated by environmental cues. Craving is an important trigger of hero... Previous research using functional MRI has shown that specific brain regions associated with drug dependence and cue-elicited heroin craving are activated by environmental cues. Craving is an important trigger of heroin relapse, and acupuncture may inhibit craving. In this study, we performed functional MRI in heroin addicts and control subjects. We compared differences in brain activation between the two groups during heroin cue exposure, heroin cue exposure plus acupuncture at the Zusanli point (ST36) without twirling of the needle, and heroin cue exposure plus acupuncture at the Zusanli point with twirling of the needle. Heroin cue exposure elicited significant activation in craving-related brain regions mainly in the frontal lobes and callosal gyri. Acupuncture without twirling did not significantly affect the range of brain activation induced by heroin cue exposure, but significantly changed the extent of the activation in the heroin addicts group. Acupuncture at the Zusanli point with twirling of the needle significantly decreased both the range and extent of activation induced by heroin cue exposure compared with heroin cue exposure plus acupuncture without twirling of the needle. These experimental findings indicate that presentation of heroin cues can induce activation in craving-related brain regions, which are involved in reward, learning and memory, cognition and emotion. Acupuncture at the Zusanli point can rapidly suppress the activation of specific brain regions related to craving, supporting its potential as an intervention for drug craving. 展开更多
关键词 ACUPUNCTURE Zusanli (ST36) heroin addiction cues induction functional MRI CRAVING twirling activation of brain regions traditional Chinese medicine neural regeneration
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A Framework of Massively Parallel Analysis of Regional Earthquake Activities 被引量:1
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作者 ZHANG Huai SHI Yaolin WU Zhongliang 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2009年第4期786-800,共15页
Recent rapid progress in cyberinfrastructure in geosciences is providing seismologists an enormous boost for addressing multi-physical phenomena of regional seismic activities. The inherent nature of their multi-scale... Recent rapid progress in cyberinfrastructure in geosciences is providing seismologists an enormous boost for addressing multi-physical phenomena of regional seismic activities. The inherent nature of their multi-scale properties, from temporal to spatial spaces, makes it inevitably to be solved using large-scale computations and distributed parallel data processing schemes. Under such circumstance, using the advanced numerical algorithms and unstructured mesh generation technologies become the obstacles for modern seismologists. The main objective of this paper is to present a framework, which includes a parallel finite element simulation and distributed data infrastructure, to address the novel algorithms, state-of-the-art modeling and their implementation in regional seismicgenic systems. We also discuss and implement this framework to analyze the strong earthquake evolution processes in the Sichuan-Yunnan region. This study is the key to long-term seismic risk by estimates, providing a platform for predictive large-scale numerical simulation modeling of regional earthquake activities. 展开更多
关键词 regional earthquake activities parallel numerical modeling initial stress field Sichuan- Yunnan area
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Different types of drug abusers prefrontal cortex activation patterns and based on machine-learning classification
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作者 Banghua Yang Xuelin Gu +3 位作者 Shouwei Gao Lin Feng Yan Ding Xu Wen Wang 《Journal of Innovative Optical Health Sciences》 SCIE EI CAS 2022年第2期83-92,共10页
Drug addiction can cause abnormal brain activation changes,which are the root cause of drug craving and brain function errors.This study enrolled drug abusers to determine the effects of different drugs on brain activ... Drug addiction can cause abnormal brain activation changes,which are the root cause of drug craving and brain function errors.This study enrolled drug abusers to determine the effects of different drugs on brain activation.A functional near-infrared spectroscopy(fNIRS)device was used for the research.This study was designed with an experimental paradigm that included the induction of resting and drug addiction cravings.We collected the fNIRS data of 30 drug users,including 10 who used heroin,10 who used Methamphetamine,and 10 who used mixed drugs.First,using Statistical Analysis,the study analyzed the activations of eight functional areas of the left and right hemispheres of the prefrontal cortex of drug addicts who respectively used heroin,Methamphetamine,and mixed drugs,including Left/Right-Dorsolateral prefrontal cortex(L/R-DLPFC),Left/Right-Ventrolateral prefrontal cortex(L/R-VLPFC),Left/Right-Fronto-polar prefrontal cortex(L/R-FPC),and Left/Right Orbitofrontal Cortex(L/R-OFC).Second,referencing the degrees of activation of oxyhaemoglobin concentration(HbO2),the study made an analysis and got the specific activation patterns of each group of the addicts.Finally,after taking out data which are related to the addicts who recorded high degrees of activation among the three groups of addicts,and which had the same channel numbers,the paper classified the different drug abusers using the data as the input data for Convolutional Neural Networks(CNNs).The average three-class accuracy is 67.13%.It is of great significance for the analysis of brain function errors and personalized rehabilitation. 展开更多
关键词 Drug addiction FNIRS MACHINE-LEARNING di®erent drug users brain regions activation
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Proactive Saudi Arabia:Actively Tackling the Regional Ever-changing Situation
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作者 Liao Baizhi 《Contemporary International Relations》 2017年第5期11-19,共9页
There is chaos in the Gulf region. Saudi Arabia in conjunction with the United Arab Emirates, Bahrain, Egypt and other gulf countries,suddenly cut off diplomatic relations with Qatar expelling diplomats and citizens, ... There is chaos in the Gulf region. Saudi Arabia in conjunction with the United Arab Emirates, Bahrain, Egypt and other gulf countries,suddenly cut off diplomatic relations with Qatar expelling diplomats and citizens, exerting blockades on land, sea and aviation on June 5, 2017, with the excuse that Qatar supports terrorism- and damages regional security. Sandi Arabia and other gulf countries have issued an ultimatum on June 23, giving Qatar to 10 days to meet their 13 requirements. For a time, the Saudi-led group became the media hot word. The Gulf, once a rare peaceful land under the impact of the Arab Spring, now falls into chaos. The GCC in fact has split. This is another major diplomatic adventure that Saudi Arabia has taken in recent years. 展开更多
关键词 Proactive Saudi Arabia Actively Tackling the regional Ever-changing Situation
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Actively Promoting Regional Space Cooperation——Vice Administrator, Loan Enjie headed a delegation to attend the Second Asia-Pacific Conference on Multilateral Cooperation in Space Technology and Applications
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作者 Zhang Lihui 《Aerospace China》 1995年第1期14-15,共2页
A Chinese delegation of 24 persons headed by Mr. Luan Enjie, Vice Administrator of China National Space Administration (CNSA) attended the Second Asia-Pacific Conference on Multilateral Cooperation in Space Technology... A Chinese delegation of 24 persons headed by Mr. Luan Enjie, Vice Administrator of China National Space Administration (CNSA) attended the Second Asia-Pacific Conference on Multilateral Cooperation in Space Technology and Applications held at Islamabad, the Capital of Pakistan from April 22 to 26, 1995. Following the First AsiaPacific Workshop held in Beijing in December, 1992, and the First Asia-Pacific Conference on Multilateral Cooperation in 展开更多
关键词 Asia Loan Enjie headed a delegation to attend the Second Asia-Pacific Conference on Multilateral Cooperation in Space Technology and Applications Vice Administrator Actively Promoting regional Space Cooperation
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Sedimentary elements,evolutions and controlling factors of the Miocene channel system:a case study of the deep-water Taranaki Basin in New Zealand
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作者 Guangxu Wang Wei Wu +5 位作者 Changsong Lin Quan Li Xiaoming Zhao Yongsheng Zhou Weiqing Liu Shiqin Liang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2023年第11期44-58,共15页
Deep-water channel systems are important petroleum reservoirs,and many have been discovered worldwide.Understanding deep-water channel sedimentary elements and evolution is helpful for deep-sea petroleum exploration a... Deep-water channel systems are important petroleum reservoirs,and many have been discovered worldwide.Understanding deep-water channel sedimentary elements and evolution is helpful for deep-sea petroleum exploration and development.Based on high-resolution 3D seismic data,the Miocene channel system in the deep-water Taranaki Basin,New Zealand,was analyzed by using seismic interpretation techniques such as interlayer attribute extraction and strata slicing.The channel system was divided into five composite channels(CC-I to CC-V)according to four secondary level channel boundaries,and sedimentary elements such as channels,slump deposits,inner levees,mass transport deposits,and hemipelagic drape deposits were identified in the channel system.The morphological characteristics of several composite channels exhibited stark variances,and the overall morphology of the composite channels changed from relatively straight to highly sinuous to relatively straight.The evolution of the composite channels involved a gradual and repeated process of erosion and filling,and the composite channels could be divided into three evolutionary stages:initial erosion-filling,later erosion-filling(multistage),and channel abandonment.The middle Miocene channel system may have formed as a consequence of combined regional tectonic activity and global climatic change,and its intricate morphological alterations may have been influenced by the channel's ability to self-regulate and gravity flow properties.When studying the sedimentary evolution of a large-scale deep-water channel system in the Taranaki Basin during the Oligocene-Miocene,which transitioned from a passive margin to plate convergence,it can be understood how tectonic activity affected the channel and can also provide a theoretical reference for the evolution of the deepwater channels in areas with similar tectonic conversion environments around the world. 展开更多
关键词 deep-water channel system channel geomorphology sedimentary evolution climate and region tectonic activities deep-water Taranaki Basin
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A Study of Solar Rotation and Differential Rotation
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作者 Zhihui Zhou 《Journal of Applied Mathematics and Physics》 2023年第11期3782-3788,共7页
The Sun has solar rotation;nevertheless, many evidences have suggested that different latitude of the Sun rotates in different speed, which is now known as differential rotation. This work calculates the solar rotatio... The Sun has solar rotation;nevertheless, many evidences have suggested that different latitude of the Sun rotates in different speed, which is now known as differential rotation. This work calculates the solar rotation speeds near the equator and 30? in the northern hemisphere using Fixed-Point Arithmetic method. The calculated results show a greater speed at the equator than the speed at 30?, indicating that the speed decreases as the latitude becomes higher. . 展开更多
关键词 SUN Differential Rotation Active Region Fixed-Point Arithmetic Method
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Activated and deactivated functional brain areas in the Deqi state: A functional MRI study 被引量:4
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作者 Yong Huang Tongjun Zeng +5 位作者 Guifeng Zhang Ganlong Li Na Lu Xinsheng Lai Yangjia Lu Jiarong Chen 《Neural Regeneration Research》 SCIE CAS CSCD 2012年第30期2362-2369,共8页
We compared the activities of functional regions of the brain in the Deqi versus non-Deqi state, as reported by physicians and subjects cludng acupuncture, Twelve healthy volunteers received sham and true needling at ... We compared the activities of functional regions of the brain in the Deqi versus non-Deqi state, as reported by physicians and subjects cludng acupuncture, Twelve healthy volunteers received sham and true needling at the Waiguan (TE5) acupoint. Real-time cerebral functional MRI showed that compared with non-sensation after sham needling, true needling activated Brodmann areas 3, 6, 8, 9, 10, 11, 13, 20, 21, 37, 39, 40, 43, and 47, the head of the caudate nucleus, the parahippocampal gyrus, thalamus and red nucleus. True needling also deactivated Brodmann areas 1,2, 3, 4, 5, 6, 7, 9. 10. 18.24.31.40 and 46. 展开更多
关键词 NEEDLING sham needling Waiguan (TE5) sham point DEQI functional MRI brain region activation DEactivation neural regeneration
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The active principle region of Buyang Huanwu decoction induced differentiation of bone marrow-derived mesenchymal stem cells into neural-like cells Superior effects over original formula of Buyang Huanwu decoction 被引量:9
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作者 Jinghui Zheng Yi Wan +4 位作者 Jianhuai Chi Dekai Shen Tingting Wu Weimin Li Pengcheng Du 《Neural Regeneration Research》 SCIE CAS CSCD 2012年第4期261-267,共7页
The present study induced in vitro-cultured passage 4 bone marrow-derived mesenchymal stem cells to differentiate into neural-like cells with a mixture of alkaloid, polysaccharide, aglycone, glycoside, essential oils,... The present study induced in vitro-cultured passage 4 bone marrow-derived mesenchymal stem cells to differentiate into neural-like cells with a mixture of alkaloid, polysaccharide, aglycone, glycoside, essential oils, and effective components of Buyang Huanwu decoction (active principle region of decoction for invigorating yang for recuperation). After 28 days, nestin and neuron-specific enolase were expressed in the cytoplasm. Reverse transcription-PCR and western blot analyses showed that nestin and neuron-specific enolase mRNA and protein expression was greater in the active principle region group compared with the original formula group. Results demonstrated that the active principle region of Buyang Huanwu decoction induced greater differentiation of rat bone marrow-derived mesenchymal stem cells into neural-like cells in vitro than the original Buyang Huanwu decoction formula. 展开更多
关键词 active principle region bone marrow-derived mesenchymal stem cells Buyang Huanwu decoction differentiation nerve cells
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Cloud Radiative Forcing in Asian Monsoon Region Simulated by IPCC AR4 AMIP Models 被引量:8
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作者 李剑东 刘屹岷 吴国雄 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2009年第5期923-939,共17页
This study examines cloud radiative forcing (CRF) in the Asian monsoon region (0° 50°N, 60° 150°E) simulated by Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4... This study examines cloud radiative forcing (CRF) in the Asian monsoon region (0° 50°N, 60° 150°E) simulated by Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) AMIP models. During boreal winter, no model realistically reproduces the larger long-wave cloud radiative forcing (LWCF) over the Tibet Plateau (TP) and only a couple of models reasonably capture the larger short-wave CRF (SWCF) to the east of the TP. During boreal summer, there are larger biases for central location and intensity of simulated CRF in active convective regions. The CRF biases are closely related to the rainfall biases in the models. Quantitative analysis further indicates that the correlation between simulated CRF and observations are not high, and that the biases and diversity in SWCF are larger than that in LWCF. The annual cycle of simulated CRF over East Asia (0°-50°N, 100°-145°E) is also examined. Though many models capture the basic annual cycle in tropics, strong LWCF and SWCF to the east of the TP beginning in early spring are underestimated by most models. As a whole, GFDL-CM2.1, MPI-ECHAM5, UKMO-HadGAM1, and MIROC3.2 (medres) perform well for CRF simulation in the Asian monsoon region, and the multi-model ensemble (MME) has improved results over the individual simulations. It is suggested that strengthening the physical parameterizations involved over the TP, and improving cumulus convection processes and model experiment design are crucial to CRF simulation in the Asian monsoon region. 展开更多
关键词 cloud radiative forcing (CRF) AMIP models Asian monsoon region Tibet Plateau (TP) active convective region
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Evidence of cortical reorganization of language networks after stroke with subacute Broca's aphasia:a blood oxygenation level dependent-functional magnetic resonance imaging study 被引量:8
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作者 Wei-hong Qiu Hui-xiang Wu +7 位作者 Qing-lu Yang Zhuang Kang Zhao-cong Chen Kui Li Guo-rong Qiu Chun-qing Xie Gui-fang Wan Shao-qiong Chen 《Neural Regeneration Research》 SCIE CAS CSCD 2017年第1期109-117,共9页
Aphasia is an acquired language disorder that is a common consequence of stroke.The pathogenesis of the disease is not fully understood,and as a result,current treatment options are not satisfactory.Here,we used blood... Aphasia is an acquired language disorder that is a common consequence of stroke.The pathogenesis of the disease is not fully understood,and as a result,current treatment options are not satisfactory.Here,we used blood oxygenation level-dependent functional magnetic resonance imaging to evaluate the activation of bilateral cortices in patients with Broca's aphasia 1 to 3 months after stroke.Our results showed that language expression was associated with multiple brain regions in which the right hemisphere participated in the generation of language.The activation areas in the left hemisphere of aphasia patients were significantly smaller compared with those in healthy adults.The activation frequency,volumes,and intensity in the regions related to language,such as the left inferior frontal gyrus(Broca's area),the left superior temporal gyrus,and the right inferior frontal gyrus(the mirror region of Broca's area),were lower in patients compared with healthy adults.In contrast,activation in the right superior temporal gyrus,the bilateral superior parietal lobule,and the left inferior temporal gyrus was stronger in patients compared with healthy controls.These results suggest that the right inferior frontal gyrus plays a role in the recovery of language function in the subacute stage of stroke-related aphasia by increasing the engagement of related brain areas. 展开更多
关键词 nerve regeneration functional magnetic resonance imaging cortical functional connectivity language regions neuroplasticity Perisylvian language regions brain activation right hemisphere picture-naming task neural regeneration
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Experimental study and simulations of infiltration in evapotranspiration landfill covers 被引量:1
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作者 Wen-xian ZHANG Zhan-yu ZHANG Kang WANG 《Water Science and Engineering》 EI CAS 2009年第3期96-109,共14页
Various cover systems have been designed for landfill sites in order to minimize infiltration (percolation) into the underlying waste. This study evaluated the soil water balance performance of evapotranspiration co... Various cover systems have been designed for landfill sites in order to minimize infiltration (percolation) into the underlying waste. This study evaluated the soil water balance performance of evapotranspiration covers (ET covers) and simulated percolation in the systems using the active region model (ARM). Experiments were conducted to measure water flow processes and water balance components in a bare soil cover and different ET covers. Results showed that vegetation played a critical role in controlling the water balance of the ET covers. In soil profiles of 60-cm depth with and without vegetation cover, the maximum soil water storage capacities were 97.2 mm and 62.8 mm, respectively. The percolation amount in the bare soil was 2.1 times that in the vegetation-covered soil. The ARM simulated percolation more accurately than the continuum model because it considered preferential flow. Numerical simulation results also indicated that using the ET cover system was an effective way of removing water through evanotransoiration, thus reducing nercolation. 展开更多
关键词 active region model evapotranspiration cover percolation control water balance
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Quasi-periodic outflows observed by the X-Ray Telescope onboard Hinode in the boundary of an active region 被引量:2
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作者 Li-Jia Guo Hui Tian Jian-Sen He 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2010年第12期1307-1314,共8页
Persistent outflows have recently been detected at the boundaries of some active regions. Although these outflows are suggested to be possible sources of the slow solar wind, the nature of these outflows is poorly und... Persistent outflows have recently been detected at the boundaries of some active regions. Although these outflows are suggested to be possible sources of the slow solar wind, the nature of these outflows is poorly understood. Through an analy- sis of an image sequence obtained by the X-Ray Telescope onboard the Hinode spacecraft, we found that quasi-periodic outflows are present in the boundary of an active region. The flows are observed to occur intermittently, often with a period of 5-10 min. The proj ected flow speed can reach more than 200 km s^-1, while its distribution peaks around 50 km s^-1. This sporadic high-speed outflow may play an important role in the mass loading process of the slow solar wind. Our results may imply that the outflow of the slow solar wind in the boundary of the active region is intermittent and quasiperiodic in nature. 展开更多
关键词 solar wind -- Sun: UV radiation -- active region
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Flux emergence in the solar active region NOAA 11158: the evolution of net current 被引量:1
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作者 Panditi Vemareddy Parameswaran Venkatakrishnan Solipuram Karthikreddy 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2015年第9期1547-1558,共12页
We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region (AR) NOAA 11158 obtained from the Helioseismic and Magnetic Image... We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region (AR) NOAA 11158 obtained from the Helioseismic and Magnetic Imager. We also discuss the relation of net current to the observed eruptive events. The AR evolved from the βγ to βγδ3 configuration over a period of six days. The AR had two sub-regions of activity with opposite chirality: one dominated by sunspot rotation producing a strong CME, and the other showing large shear motions producing a strong flare. The net current in each polarity over the CME producing sub-region increased to a maximum and then decreased when the sunspots were separated. The time profile of net current in this sub-region followed the time profile of the rotation rate of the south-polarity sunspot in the same sub-region. The net current in the flaring sub-region showed a sudden increase at the time of the strong flare and remained unchanged until the end of the observation, while the sunspots maintained their close proximity. The systematic evo- lution of the observed net current is seen to follow the time evolution of total length of strongly sheared polarity inversion lines in both of the sub-regions. The observed photospheric net current could be explained as an inevitable product of the emergence of a twisted flux rope, from a higher pressure confinement below the photosphere into the lower pressure environment of the photosphere. 展开更多
关键词 Sun:active regions -- magnetic fields -- activity -- coronal mass ejec-tions -- non-potentiality -- electric current
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Evolution of a Long-lived Sunspot Group and Its Associated Solar-terrestrial Events 被引量:1
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作者 Gui-QingZhang Li-RongTian 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2005年第1期77-86,共10页
A long-lived sunspot group (AR9604) on the south hemisphere that lasted five solar rotations and produced some strong bursts is analyzed. The focus is on its evolving features. Its whole life was successfully maintain... A long-lived sunspot group (AR9604) on the south hemisphere that lasted five solar rotations and produced some strong bursts is analyzed. The focus is on its evolving features. Its whole life was successfully maintained by four Emerging Flux Regions (EFRs). Apart from the one that lasted only a short time and did not produce any bursts, the other three EFRs have the following common features: (1) A positive writhe of magnetic flux tubes and a twist of the field lines of the same sign, indicating kink instability. (2) A clockwise rotation and a high tilt because the writhe was right-handed. (3) A compact 'island δ' structure of the sunspot group indicating concentrated kink instability. Since magnetic reconnection easily occurs at the kinked point of a very kink-unstable flux tube, these features should be the inducement of the strong bursts. 展开更多
关键词 Sun - active region evolution
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Magnetic Field Strengths and Structures from Radio Observations of Solar Active Regions 被引量:1
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作者 Chang-XiZhang G.B.Gelfreikh 《Chinese Journal of Astronomy and Astrophysics》 CSCD 北大核心 2002年第3期266-276,共11页
Radio observations of some active regions (ARs) obtained with the Nobeyama radioheliograph at λ=1.76 cm are used for estimating the magnetic field strength in the upper chromosphere, based on thermal bremsstrahlung. ... Radio observations of some active regions (ARs) obtained with the Nobeyama radioheliograph at λ=1.76 cm are used for estimating the magnetic field strength in the upper chromosphere, based on thermal bremsstrahlung. The results are compared with the magnetic field strength in the photosphere from observations with the Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observing Station of Beijing Astronomical Observatory. The difference in the magnetic field strength between the two layers seems reasonable. The solar radio maps of active regions obtained with the Nobeyama radioheliograph, both in total intensity (I-map) and in circular polarizations (V-map), are compared with the optical magnetograms obtained with the SMFT. The comparison between the radio map in circular polarization and the longitudinal photospheric magnetogram of a plage region suggests that the radio map in circular polarization is a kind of magnetogram of the upper chromosphere. The comparison of the radio map in total intensity with the photo-spheric vector magnetogram of an AR shows that the radio map in total intensity gives indications of magnetic loops in the corona, thus we have a method of defining the coronal magnetic structure from the radio I-maps at λ=1.76 cm. Analysing the I-maps, we identified three components: (a) a compact bright source; (b) a narrow elongated structure connecting two main magnetic islands of opposite polarities (observed in both the optical and radio magnetograms); (c) a wide, diffuse, weak component that corresponds to a wide structure in the solar active region which shows in most cases an S or a reversed S contour, which is probably due to the differential rotation of the Sun. The last two components suggest coronal loops on different spatial scales above the neutral line of the longitudinal photospheric magnetic field. 展开更多
关键词 Sun: active regions - Sun: magnetic fields - Sun: optical observation - Sun: radio observation
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Spectral Feature Analysis of Semiconductor Thin Disk Laser 被引量:1
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作者 (HE Chun-feng1, QIN Li2, LI Jun1, CHENG Li-wen1, LIANG Xue-mei1, NING Yong-qiang2, WANG Li-jun2 1. Key Laboratary of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences,Changchun 130033, China Graduate School of the Chinese Academy of Sciences, Beijing 100049, China 2. Key Laboratary of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033,China.) 《光机电信息》 2007年第12期19-25,共7页
The semiconductor thin disk laser is a new type of semiconductor laser. This work gives the basic operation function of the semiconductor disk laser, and analyses the heat effect by the experimentally measured photolu... The semiconductor thin disk laser is a new type of semiconductor laser. This work gives the basic operation function of the semiconductor disk laser, and analyses the heat effect by the experimentally measured photoluminescence spectrum of the laser chip at different pump power and different temperatures. We can see that: with increasing pump power, the thermal effect of the gain material becomes seriously and causes the saturation of carrier lifetime, so the electron-hole pair created in the absorbtion layer has no enough time to rate to one of the wells, and the non-radiative recombination happens in the barrier. When the thermal effect becomes stronger, the chip will be not lasing. This phenomenon is from the smaller energy offset between barrier and quantum well. We optimize the original structure design and experimental technology. A non-absorbing AlGaAs layer which is transparent to the pumping and laser wavelength is added to confine the carriers in the quantum wells. At the same time a DBR with double reflecting band is induced to improve the absorbing efficiency of the pumping light. The single QW is replaced by the three narrow QWs. This three QWs structure can add the quantum state of QW, increase the recombination probability of carriers in the QWs and reduce the heat effect. The chemical etching equipment is also improved to control the surface unevenness to be within 50 nm. 展开更多
关键词 thin disk laser heat effect PL spectrum active region heat removal GAIN BARRIER spectral shift
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Texture Image Segmentation Based on Nonlinear Diffusion
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作者 ZHANG Yu 《Geo-Spatial Information Science》 2008年第1期38-42,共5页
A texture image segmentation based on nonlinear diffusion is presented. The scale of texture can be measured during the process of nonlinear diffusion. A smooth 5-channel vector image with edge preserved, which is com... A texture image segmentation based on nonlinear diffusion is presented. The scale of texture can be measured during the process of nonlinear diffusion. A smooth 5-channel vector image with edge preserved, which is composed of intensity, scale and orientation of texture image, can be achieved by coupled nonlinear diffusion. A multi-channel statistical region active contour is employed to segment this vector image. The method can be seen as a kind of unsupervised segmentation because parameters are not sensitive to different texture images. Experimental results show its high efficiency in the semiautomatic extraction of texture image. 展开更多
关键词 texture image segmentation nonlinear diffusion statistical region active contour
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GaN-based violet laser diodes grown on free-standing GaN substrate
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作者 张立群 张书明 +5 位作者 江德生 王辉 朱建军 赵德刚 刘宗顺 杨辉 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第12期5350-5353,共4页
A violet laser diode (LD) structure is grown on a free-standing c-plane GaN substrate and 4 μm×800μm ridge waveguide LDs are fabricated. The electrical and the optical characteristics of LDs under different f... A violet laser diode (LD) structure is grown on a free-standing c-plane GaN substrate and 4 μm×800μm ridge waveguide LDs are fabricated. The electrical and the optical characteristics of LDs under different facet-coating and chip-mounting conditions are investigated under pulse mode operation. The active region temperatures of p-side up and p-side down mounted LDs are calculated with different injection currents. The calculated thermal resistances of p-side up and p-side down mounted LDs are 4.6 K/W and 3 K/W, respectively. The threshold current of the p-side down mounted LD is much lower than that of the p-side up mounted LD. The blue shift of the emission wavelength with increasing injection current is observed only for the LD with p-side down mounting configuration, due to the more efficient heat dissipation. 展开更多
关键词 GaN laser diode mounting configuration active region temperature
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