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冷战后日本“北方领土”政策:演变、特征及影响 预览
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作者 陈梦莉 《东北亚学刊》 2020年第1期133-144,151,152,共14页
冷战后,日本逐渐采取了不同于冷战时期的“北方领土”政策。在两次领土政策强硬时期,日本政府都坚持“政经不可分”原则,试图利用自身经济优势迫使俄方在领土问题上让步;在两次领土政策缓和时期,日本政府试图利用首脑外交和经济手段,促... 冷战后,日本逐渐采取了不同于冷战时期的“北方领土”政策。在两次领土政策强硬时期,日本政府都坚持“政经不可分”原则,试图利用自身经济优势迫使俄方在领土问题上让步;在两次领土政策缓和时期,日本政府试图利用首脑外交和经济手段,促进领土问题的解决。其中,外部环境和国内领土争论是日本采取不同于冷战时期“北方领土”政策的重要原因。此外,不同领土政策对解决领土问题和处理日俄双边关系产生不同的影响,如何把握日本政府制定“北方领土”政策的规律和特点,对于预测日本政府未来的领土政策有重要作用。 展开更多
关键词 “北方领土” 强硬 缓和 日俄关系 战后外交总决算
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Diagnosis and treatment of heart failure with preserved left ventricular ejection fraction 预览
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作者 Robert J Henning 《世界心脏病学杂志:英文版(电子版)》 2020年第1期7-25,共19页
Nearly six million people in United States have heart failure.Fifty percent of these people have normal left ventricular(LV)systolic heart function but abnormal diastolic function due to increased LV myocardial stiffn... Nearly six million people in United States have heart failure.Fifty percent of these people have normal left ventricular(LV)systolic heart function but abnormal diastolic function due to increased LV myocardial stiffness.Most commonly,these patients are elderly women with hypertension,ischemic heart disease,atrial fibrillation,obesity,diabetes mellitus,renal disease,or obstructive lung disease.The annual mortality rate of these patients is 8%-12%per year.The diagnosis is based on the history,physical examination,laboratory data,echocardiography,and,when necessary,by cardiac catheterization.Patients with obesity,hypertension,atrial fibrillation,and volume overload require weight reduction,an exercise program,aggressive control of blood pressure and heart rate,and diuretics.Miniature devices inserted into patients for pulmonary artery pressure monitoring provide early warning of increased pulmonary pressure and congestion.If significant coronary heart disease is present,coronary revascularization should be considered. 展开更多
关键词 Diastolic heart failure Myocardial stiffness Incomplete left ventricular relaxation Echocardiographic heart failure criteria Pulmonary artery pressure monitoring Drug treatment
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Main α relaxation and slow β relaxation processes in a La30Ce30Al15Co25 metallic glass
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作者 J.C. Qiao Y.H. Chen +2 位作者 R. Casalini J.M. Pelletier Y. Yao 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第6期982-986,共5页
Dynamic relaxation processes are fundamental to understand the mechanical and physical properties of metallic glasses. In the current work, mechanical relaxations in a La30Ce30Al15Co25 bulk metallic glass were probed ... Dynamic relaxation processes are fundamental to understand the mechanical and physical properties of metallic glasses. In the current work, mechanical relaxations in a La30Ce30Al15Co25 bulk metallic glass were probed by dynamic mechanical analysis. In contrast to many metallic glasses, La30Ce30Al15Co25 metallic glass shows a pronounced slow β relaxation peak. Physical aging below the glass transition temperature Tgleads to an increase of the apparent activation energy and a decrease of the slow β relaxation magnitude. The correlation between the slow β relaxation and the main α relaxation is discussed. 展开更多
关键词 MECHANICAL RELAXATION Dynamic MECHANICAL RELAXATION α RELAXATION β RELAXATION Physical AGING
Intrinsic transverse relaxation mechanisms of polarized alkali atoms enclosed in radio-frequency magnetometer cell
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作者 傅杨颖 袁杰 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第9期385-390,共6页
The intrinsic transverse relaxation mechanisms of polarized alkali atoms enclosed in the radio-frequency magnetometer cell are investigated.The intrinsic transverse relaxation rate of cesium atoms as a function of cel... The intrinsic transverse relaxation mechanisms of polarized alkali atoms enclosed in the radio-frequency magnetometer cell are investigated.The intrinsic transverse relaxation rate of cesium atoms as a function of cell temperature is obtained.The absorption of alkali atoms by the glass wall and the reservoir effect are the main error factors which contribute to the disagreements between theory and experiments.A modified relaxation model is presented, in which both the absorption of alkali atoms by the glass wall and the reservoir effect are included.This study provides a more accurate description of the intrinsic transverse relaxation mechanisms of polarized alkali atoms, and enlightens the optimization of the cell design. 展开更多
关键词 INTRINSIC TRANSVERSE RELAXATION modified RELAXATION model absorption of alkali ATOMS reservoir effect
缝合打结过程中手术缝合线力学性能研究
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作者 张力 戴安 +1 位作者 李炜 周仲荣 《生物医学工程学杂志》 EI CAS CSCD 北大核心 2019年第3期386-392,400共8页
在临床操作中,手术缝合线的断裂、结的滑脱和缝合线对组织的撕裂是造成伤口缝合失效的主要原因。基于此,本文在生物材料试验机上模拟缝合打结过程,研究了丝线、聚乳糖酸910缝合线和聚丙烯缝合线打结前后的拉伸、松弛和线-线界面的摩擦... 在临床操作中,手术缝合线的断裂、结的滑脱和缝合线对组织的撕裂是造成伤口缝合失效的主要原因。基于此,本文在生物材料试验机上模拟缝合打结过程,研究了丝线、聚乳糖酸910缝合线和聚丙烯缝合线打结前后的拉伸、松弛和线-线界面的摩擦性能。结果表明,打结使缝合线的拉伸性能降低。其中聚乳糖酸910缝合线拉伸强度最大,聚丙烯缝合线延伸率最大;在松弛过程中,缝合线在初始2h松弛量最大,松弛量从小到大为:聚乳糖酸910缝合线、丝线、聚丙烯缝合线。涂层和单丝结构均能有效降低缝合线表面粗糙度,从而减小线-线界面的摩擦力;线-线界面的摩擦力随载荷增加而增加,而与摩擦速度无关。研究结果为优化缝合线设计和缝合打结操作提供了重要的理论基础。 展开更多
关键词 手术缝合线 表面形貌 拉伸 松弛 摩擦特性
A Comparison between Sabra and Alfa Fibers in Rubber Biocomposites
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作者 Wafa Ouarhim Hamid Essabif +3 位作者 Mohammed-Ouadi Bensalah Denis Rodrigue Rachid Bouhfid Abou el kacem Qaiss 《仿生工程学报:英文版》 SCIE EI CSCD 2019年第4期754-767,共14页
The main objective of this investigation is to valorize a Moroccan crop residue(Sabra fibers,Agave Americana L.)and to compare with Alfa fibers(,Stipa tenacissima L.)as reinforcement in an elastomeric matrix in term o... The main objective of this investigation is to valorize a Moroccan crop residue(Sabra fibers,Agave Americana L.)and to compare with Alfa fibers(,Stipa tenacissima L.)as reinforcement in an elastomeric matrix in term of the relaxation properties,mechanical and rheological properties.The preparation and properties of these two natural fibers embedded in Styrene-Butadiene Rubber(SBR)are presented with and without the addition of Styrene-Ethylene-Butadiene-Styrene grafted with Maleic Anhydride(SEBS-g-MA)as a coupling agent.Five different series(SBR,SBR/Alfa,SBR/Alfa/SEBS,SBR/Sabra and SBR/Sabra/SEBS)were compounded by extrusion and compression molding.As a result,the addition of the coupling agent in the elastomeric matrix improves the relaxation properties,mechanical and rheological properties.Moreover,Sabra fibers show the good results compared to Alfa fibers.Finally,the Zener model was used to determine the rheological time response of the composites.A good agreement between the experimental data and the model was observed(R^2=0.99). 展开更多
关键词 Sabra fibers ALFA fibers SBR BIOCOMPOSITE RELAXATION mechanical and RHEOLOGICAL properties Zener model
Use of music during colonoscopy: An updated meta-analysis of randomized controlled trials 预览
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作者 Ryan D Heath Nasim Parsa +7 位作者 Michelle L Matteson-Kome Victoria Buescher Sami Samiullah Douglas L Nguyen Veysel Tahan Yezaz A Ghouri Srinivas R Puli Matthew L Bechtold 《世界荟萃分析杂志》 2019年第9期428-435,共8页
BACKGROUND Music seems to be beneficial in multiple clinical areas.Colonoscopy is a stressful event for patients,especially with conscious sedation.Music during colonoscopy has been evaluated in multiple randomized co... BACKGROUND Music seems to be beneficial in multiple clinical areas.Colonoscopy is a stressful event for patients,especially with conscious sedation.Music during colonoscopy has been evaluated in multiple randomized controlled trials(RCTs)with varied results.Even meta-analyses on the subject over the years have yielded inconsistent conclusions.Therefore,we conducted an up-to-date meta-analysis regarding music during colonoscopy.AIM To assess the effects of music played during colonoscopy on patients’perspectives and sedation requirements.METHODS Multiple large databases were aggressively searched(November 2018).RCTs comparing music to without music during colonoscopy on adult patients were included.Pooled estimates were calculated for sedative medication doses,total procedure time,and patients’experience,willingness to repeat procedure,and pain scores using odds ratio(OR)and mean difference(MD)with random effects model.RESULTS Eleven studies(n=988)were included.Music during colonoscopy showed a statistically significant reduction in procedure times(MD:-2.3 min;95%CI:-4.13 to-0.47;P=0.01)and patients’pain(MD:-1.26;95%CI:-2.28 to-0.24;P=0.02)while improving patients’experience(MD:-1.11;95%CI:-1.7 to-0.53;P<0.01)as compared to no music.No statistically significant differences were observed between music and no music during colonoscopy for midazolam(MD:-0.4 mg;95%CI:-0.9 to 0.09;P=0.11),meperidine(MD:-3.06 mg;95%CI:-10.79 to 4.67;P=0.44),or patients’willingness to repeat the colonoscopy(OR:3.89;95%CI:0.76 to 19.97;P=0.1).CONCLUSION Music appears to improve overall patient experience while reducing procedure times and patient pain.Therefore,music,being a non-invasive intervention,should be strongly considered during colonoscopy. 展开更多
关键词 COLONOSCOPY MUSIC RELAXATION META-ANALYSIS
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Study on Postseismic Impact of Wenchuan Earthquake on the Sichuan-Yunnan Region Based on Three-Dimensional Viscoelastic Finite Element Method 预览
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作者 JIANG Fengyun ZHU Liangyu LI Yujiang 《中国地震研究:英文版》 CSCD 2019年第4期632-647,共16页
Based on the lateral segmentation and vertical stratification characteristics of the crustal medium in Sichuan-Yunnan region,and the asymmetry of the static dislocations on the coseismic fault plane of the Wenchuan M_... Based on the lateral segmentation and vertical stratification characteristics of the crustal medium in Sichuan-Yunnan region,and the asymmetry of the static dislocations on the coseismic fault plane of the Wenchuan M_S8.0 earthquake,we built a three-dimensional viscoelastic finite element model of the crust in the Sichuan-Yunnan region.The postseismic impact of the Wenchuan M_S8.0 earthquake on the Sichuan-Yunnan region was studied.The results show that:①The far-field horizontal deformation caused by the viscoelastic relaxation of the medium in the 10 years after the earthquake is about 0-20 mm within the Sichuan-Yunnan diamond-shaped block,which has a greater influence on north side and smaller on south side.②In the 10 years after the earthquake,the far-field vertical deformation caused by the viscoelastic relaxation effect of the medium is small,and it shows an increase of about 0-4 mm in most areas of the Sichuan-Yunnan diamond-shaped block.③The Xianshuihe fault and the eastern segment of the East Kunlun fault,which are close to the seismogenic fault,show a high gradient on deformation fields after the earthquake.④In order to compare with the strong earthquake activity in the SichuanYunnan region after the Wenchuan earthquake,the horizontal stress state and the Coulomb failure stress change of the active block boundary are also calculated.From the spatial distribution of the coseismic and postseismic displacement field,the fault activity characteristics reflected by the stress state and the stress loading of the fault layer reflected by the Coulomb failure stress change,there is a certain correlation with the spatial distribution of strong earthquake activity in this region. 展开更多
关键词 Wenchuan M_S8.0 earthquake Finite element Viscoelastic relaxation Sichuan-Yunnan region
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Modelling Debye Dielectric Relaxation in Monohydroxy Alcohols
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作者 王丽娜 赵兴宇 黄以能 《中国物理快报:英文版》 SCIE CAS CSCD 2019年第9期72-76,共5页
The Debye relaxation of dielectric spectroscopy exists extensively in monohydroxy alcohols.We model the relaxation based on the infinite-pseudospin-chain Ising model and the Glauber dynamics,and the corresponding comp... The Debye relaxation of dielectric spectroscopy exists extensively in monohydroxy alcohols.We model the relaxation based on the infinite-pseudospin-chain Ising model and the Glauber dynamics,and the corresponding complex permittivity is obtained.The model results are in good agreement with the experimental data of 3,7-dimethyl-1-octanol,2-ethyl-1-hexanol and 5-methyl-2-hexanol in a wide temperature range.Moreover,in the model parameters,the sum of the mean-field interaction energy and two times the orientation is nearly twice the hydrogen bond energy,which further states the rationality of this model. 展开更多
关键词 ARRHENIUS MODELLING DEBYE Dielectric RELAXATION in Monohydroxy ALCOHOLS
Solution structure of the RNA recognition domain of METTL3-METTL14 N^6-methyladenosine methyltransferase
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作者 Jinbo Huang Xu Dong +8 位作者 Zhou Gong Ling-Yun Qin Shuai Yang Yue-Ling Zhu Xiang Wang Delin Zhang Tingting Zou Ping Yin Chun Tang 《蛋白质与细胞:英文版》 SCIE CAS CSCD 2019年第4期272-284,共13页
N^6-methyladenosine(m6A),a ubiquitous RNA modification,is installed by METTL3-METTL14 complex.The structure of the heterodimeric complex between the methyltransferase domains(MTDs)of METTL3 and METTL14 has been previo... N^6-methyladenosine(m6A),a ubiquitous RNA modification,is installed by METTL3-METTL14 complex.The structure of the heterodimeric complex between the methyltransferase domains(MTDs)of METTL3 and METTL14 has been previously determined.However,the MTDs alone possess no enzymatic activity.Here we present the solution structure for the zinc finger domain(ZFD)of METTL3,the inclusion of which fulfills the methyltransferase activity of METTL3-METTL14.We show that the ZFD specifically binds to an RNA containing 5'-GGACU-3'consensus sequence,but does not to one without.The ZFD thus serves as the target recognition domain,a structural feature previously shown for DNA methyltransferases,and cooperates with the MTDs of METTL3-METTL14 for catalysis.However,the interaction between the ZFD and the specific RNA is extremely weak,with the binding affinity at several hundred micromolar under physiological conditions.The ZFD contains two CCCH-type zinc fingers connected by an anti-parallel P-sheet.Mutational analysis and NMR titrations have mapped the functional interface to a contiguous surface.As a division of labor,the RNA-binding interface comprises basic residues from zinc finger 1 and hydrophobic residues fromβ-sheet and zinc finger 2.Further we show that the linker between the ZFD and MTD of METTL3 is flexible but partially folded,which may permit the cooperation between the two domains during catalysis.Together,the structural characterization of METTL3 ZFD paves the way to elucidate the atomic details of the entire process of RNA m6A modification. 展开更多
关键词 RNA modification N^6-methyladenosine METTL3 target recognition DOMAIN zinc FINGER PARAMAGNETIC RELAXATION enhancement
Entrainment range affected by the heterogeneity in the amplitude relaxation rate of suprachiasmatic nucleus neurons
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作者 顾长贵 王萍 杨会杰 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第1期663-668,共6页
Adaption of circadian rhythms in behavioral and physiological activities to the external light–dark cycle is achieved through the main clock,i.e.,the suprachiasmatic nucleus(SCN)of the brain in mammals.It has been fo... Adaption of circadian rhythms in behavioral and physiological activities to the external light–dark cycle is achieved through the main clock,i.e.,the suprachiasmatic nucleus(SCN)of the brain in mammals.It has been found that the SCN neurons differ in the amplitude relaxation rate,which represents the rigidity of the neurons to the external amplitude disturbance.Thus far,the appearance of that difference has not been explained.In the present study,an alternative explanation based on the Poincare′model is given which takes into account the effect of the difference in the entrainment range of the SCN.Both our simulation results and theoretical analyses show that the largest entrainment range is obtained with suitable difference in the case that only a part of SCN neurons are sensitive to the light information.Our findings may give an alternative explanation for the appearance of that difference(heterogeneity)and shed light on the effects of the heterogeneity in the neuronal properties on the collective behaviors of the SCN neurons. 展开更多
关键词 AMPLITUDE RELAXATION rate ENTRAINMENT RANGE HETEROGENEITY
A Flexible Space-Time Tradeoff on Hybrid Index with Bicriteria Optimization
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作者 Xingshen Song Yuexiang Yang Yu Jiang 《清华大学学报自然科学版(英文版)》 EI CAS CSCD 2019年第1期106-122,共17页
Inverted indexes are widely adopted in the vast majority of information systems.Growing requirements for efficient query processing have motivated the development of various compression techniques with different space... Inverted indexes are widely adopted in the vast majority of information systems.Growing requirements for efficient query processing have motivated the development of various compression techniques with different space- time characteristics.Although a single encoder yields a relatively stable point in the space-time tradeoff curve, flexibly transforming its characteristic along the curve to fit different information retrieval tasks can be a better way to prepare the index.Recent research comes out with an idea of integrating different encoders within the same index, namely,exploiting access skewness by compressing frequently accessed regions with faster encoders and rarely accessed regions with succinct encoders,thereby improving the efficiency while minimizing the compressed size. However,these methods are either inefficient or result in coarse granularity.To address these issues,we introduce the concept of bicriteria compression,which aims to formalize the problem of optimally trading the compressed size and query processing time for inverted index.We also adopt a Lagrangian relaxation algorithm to solve this problem by reducing it to a knapsack-type problem,which works in O(n logn)time and O(n)space,with a negligible additive approximation.Furthermore,this algorithm can be extended via dynamic programming pursuing improved query efficiency.We perform an extensive experiment to show that,given a bounded time/space budget,our method can optimally trade one for another with more efficient indexing and query performance. 展开更多
关键词 INVERTED index BICRITERIA compression LAGRANGIAN RELAXATION
Numerical Investigation of Lid-Driven Deep Cavity with Local Grid Refinement of MRT-LBM 预览
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作者 Dongdong Wan Guichao Wang Songying Chen 《北京理工大学学报:英文版》 EI CAS 2019年第3期536-548,共13页
In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the ca... In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the cases, the aspect ratio and Reynolds number are set as 1.5 and 3.200, respectively. First, the applied method is validated by comparing it with two reported works, with which agreements are reached. Then, six separate degrees of local grid refinement at the upper left corner, i.e. purely coarse grid, including 1/64, 1/32, 1/16, 1/8, 1/4 refinements of the lattice number in the width direction have been studied in detail. The results give the following indications:① The refinement degrees lower than 1/8 produce similar results;② For single corner refinement, 1/4 refinement is adequate for clearing the noises in the singularity zone to a large extent;③ New noise around the interface between coarse and fine zones are introduced by local grid refinement. Finally, refinement of entire subzone neighboring the lid is examined to avoid introducing new noises and it has been found effective. 展开更多
关键词 numerical investigation lid-driven DEEP CAVITY local grid REFINEMENT lattice BOLTZMANN method (LBM) multiple relaxation time (MRT)
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Semidefinite relaxation aided noncoherent detection in two-way relay transmission
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作者 Chan-fei WANG Ji-ai HE +1 位作者 Wei-fang WANG Ya-mei XU 《信息与电子工程前沿:英文版》 SCIE EI CSCD 2019年第9期1259-1265,共7页
A high-performance noncoherent transmission scheme is proposed in the broadcasting phase of a twoway relay transmission(TWRT),where multiple-symbol differential detection(MSDD)is performed because of its excellent det... A high-performance noncoherent transmission scheme is proposed in the broadcasting phase of a twoway relay transmission(TWRT),where multiple-symbol differential detection(MSDD)is performed because of its excellent detection performance with no channel estimation.Specifically,the generalized likelihood ratio test aided MSDD(GLRT-MSDD)is developed for the down-link.Furthermore,GLRT-MSDD is reformulated and a semidefinite relaxation aided MSDD(SDR-MSDD)is proposed.The reformulation of GLRT-MSDD to SDR-MSDD is desirable owing to its reduced complexity.Performance analysis and the simulations validate that the proposed SDR-MSDD provides the bit-error-rate performance close to that of GLRT-MSDD with reasonable complexity in TWRT. 展开更多
关键词 Multiple-symbol differential detection Generalized LIKELIHOOD ratio test SEMIDEFINITE RELAXATION Two-way RELAY TRANSMISSION
Rate-Dep endent Characteristic of Relaxation Time of Concrete
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作者 Hui Song Jiankang Chen +2 位作者 Cheng Qian Yunfeng Lv Yonghui Cao 《固体力学学报:英文版》 SCIE EI CSCD 2019年第1期69-80,共12页
This study focused on the rate-dependent relaxation time of concrete using the split Hopkinson pressure bar test and the ultrasonic technique.Based on the experimental results,and considering the viscous effect in con... This study focused on the rate-dependent relaxation time of concrete using the split Hopkinson pressure bar test and the ultrasonic technique.Based on the experimental results,and considering the viscous effect in concrete,the viscoelastic stress-strain relationship was established in terms of the principles of irreversible thermodynamics and the generalized Onsager's principle,providing the convergence of an iterative scheme in terms of the Lipschitz's condition.It was found that the relaxation time of concre te depends on the strain rate.Furt her more,considering the state equations and damage evolution,a nonlinear viscoelastic constitutive model of concrete coupling damage was proposed.Compared with the experimental results,this model could better characterize the strengthening and softening characteristics of concrete prior to and beyond the strength limit.Further analysis indicated that the viscous effect is dominantly caused by the C-S-H in concrete. 展开更多
关键词 CONCRETE CONSTITUTIVE RELATION VISCOELASTICITY RELAXATION time Damage evolution
New Economy in China:Emerging,Operation and Regulatory Reform 预览
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作者 戚聿东 李颖 《中国经济学人:英文版》 2019年第2期2-13,共12页
In the new normal,China must develop a new economy in order to foster new engines of growth.The new economy differs from the traditional economy in many respects,such as its underlying drivers and technical,industrial... In the new normal,China must develop a new economy in order to foster new engines of growth.The new economy differs from the traditional economy in many respects,such as its underlying drivers and technical,industrial and organizational characteristics.This paper reveals six aspects of the mechanism of the new economy,including firm entry strategy,new opportunities,market demand,transition of production factors,industry support and the role of the government.In addition,the operation of the new economy is explained in terms of its underlying drivers,internal operations and external environment.In the new economy,fundamental changes have occurred in monopoly,information asymmetry,externalities,public goods and information security necessitating a new regulatory approach.Regulatory reform is therefore inevitable.China should steadfastly transition from regulatory tightening to deregulation,from economic regulation to social regulation,from discriminatory regulation to fair competition,from the positive list to the negative list,from ex-ante review and approval to ex-post supervision,and from specialized regulation to integrated regulation.Innovations must be encouraged through the use of “regulatory sandboxes.” 展开更多
关键词 new ECONOMY INNOVATION prudent REGULATION REGULATORY RELAXATION
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线性互补问题的广义松弛两步模基矩阵分裂迭代法 预览
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作者 彭小飞 《华南师范大学学报:自然科学版》 CAS 北大核心 2019年第4期93-99,共7页
将松弛策略引入到与线性互补问题等价的广义隐式定点迭代方程,建立了求解线性互补问题的广义松弛两步模基矩阵分裂迭代法,将已有的松弛两步模基矩阵分裂迭代法扩展到了更一般的情形;当系数矩阵为H+-矩阵时,利用H+-矩阵的特殊性质,给出... 将松弛策略引入到与线性互补问题等价的广义隐式定点迭代方程,建立了求解线性互补问题的广义松弛两步模基矩阵分裂迭代法,将已有的松弛两步模基矩阵分裂迭代法扩展到了更一般的情形;当系数矩阵为H+-矩阵时,利用H+-矩阵的特殊性质,给出了新方法的收敛性分析.数值结果表明:依据迭代次数和CPU时间,由新方法所导出的新的广义方法比已有的广义模基矩阵分裂迭代法和广义两步模基矩阵分裂迭代法更有效. 展开更多
关键词 线性互补问题 矩阵分裂 两步迭代方法 松弛 收敛
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Magnetic resonance imaging of the zone of calcified cartilage in the knee joint using 3-dimensional ultrashort echo time cones sequences
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作者 Jin Liu Yang Wei +3 位作者 Ya-Jun Ma Yan-Chun Zhu Quan Zhou Ying-Hua Zhao 《中华医学杂志:英文版》 SCIE CAS CSCD 2019年第5期562-568,共7页
Background: The zone of calcified cartilage (ZCC) plays an important role in the pathogenesis of osteoarthritis (OA) but has never been imaged in vivo with magnetic resonance (MR) imaging techniques. We investigated t... Background: The zone of calcified cartilage (ZCC) plays an important role in the pathogenesis of osteoarthritis (OA) but has never been imaged in vivo with magnetic resonance (MR) imaging techniques. We investigated the feasibility of direct imaging of the ZCC in both cadaveric whole knee specimens and in vivo healthy knees using a 3-dimensional ultrashort echo time cones (3D UTE-Cones) sequence on a clinical 3T scanner. Methods: In all, 12 cadaveric knee joints and 10 in vivo healthy were collected. At a 3T MR scanner with an 8-channel knee coil, a fat-saturated 3D dual-echo UTE-Cones sequence was used to image the ZCC, following with a short rectangular pulse excitation and 3D spiral sampling with conical view ordering. The regions of interests (ROIs) were delineated by a blinded observer. Singlecomponent T2* and T2 values were calculated from fat-saturated 3D dual-echo UTE-Cones and a Carr-Purcell-Meiboom-Gill (T2 CPMG) data using a semi-automated MATLAB code. Results: The single-exponential fitting curve of ZCC was accurately obtained with R2 of 0.989. For keen joint samples, the ZCC has a short T2* ranging from 0.62 to 2.55 ms, with the mean ±standard deviation (SD) of 1.49 ±0.66 ms, and with 95% confidence intervals (CI) of 1.20-1.78 ms. For volunteers, the short T2* ranges from 0.93 to 3.52ms, with the mean±SD of 2.09±0.56 ms, and the 95% CI is 1.43 to 2.74ms in ZCC. Conclusions: The high-resolution 3D UTE-Cones sequence might be used to directly image ZCC in the human knee joint on a clinical 3T scanner with a scan time of more than 10 min. Using this non-invasive technique, the T2* relaxation time of the ZCC can be further detected. 展开更多
关键词 ULTRASHORT echo TIME T2* relaxation TIME ZONE of CALCIFIED CARTILAGE ARTICULAR CARTILAGE
基于改进的多项近似法解玻尔兹曼方程研究电子在交叉电磁场下的弛豫特性
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作者 蔡新景 王新新 +2 位作者 邹晓兵 鲁志伟 孙宇 《中国电机工程学报》 EI CSCD 北大核心 2019年第5期1526-1532,共7页
研究等离子体的电子弛豫过程对于等离子体反应器、等离子体光源和气体激光器等研究具有重要的意义。为了研究电子在交叉电磁场下弛豫特性,文中采用改进的多项近似法解玻尔兹曼方程计算电子输运和弛豫特性。首先对Reid非弹性碰撞模型进... 研究等离子体的电子弛豫过程对于等离子体反应器、等离子体光源和气体激光器等研究具有重要的意义。为了研究电子在交叉电磁场下弛豫特性,文中采用改进的多项近似法解玻尔兹曼方程计算电子输运和弛豫特性。首先对Reid非弹性碰撞模型进行电子输运系数计算,发现:当约化电场强度E/n0为12Td时,lmax增加到7所有输运系数可以达到4位数字精度;当增加约化磁场强度B/n0为500Hx而保持约化电场强度不变时,lmax增加到2所有输运系数就能达到4位数字精度,表明磁场能降低电子速度的各向异性。与Ness和White等人的计算结果进行比较,验证了采用改进的多项近似法解玻尔兹曼方程计算电子输运系数的有效性。接着计算了电子的弛豫特性,发现:瞬时施加磁场时,电子平均能量ε随着时间呈单调变化,而体漂移速度WBz、体漂移速度WBx和扩散系数n0Dii均随着时间呈衰减震荡变化;电子弛豫过程至少有3个典型弛豫时间:电子回旋时间γg、动量弛豫时间γm和能量弛豫时间γe,且满足γg<γm<γe;瞬时施加磁场后,体漂移速度WBx响应最快,体漂移速度WBz和扩散系数n0Dii响应次之,电子平均能量ε响应最慢;当约化磁场强度B/n0为500 Hx时,体漂移速度WBz在第一个震荡周期与E同方向,扩散系数n0Dxx出现负扩散现象。 展开更多
关键词 多项近似 玻尔兹曼方程 电子输运系数 弛豫 交叉电磁场 电子回旋周期 负扩散
Mechanical Relaxation of a Ti36.2Zr30.3Cu8.3Fe4Be21.2 Bulk Metallic Glass:Experiments and Theoretical Analysis
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作者 J.C.Qiao Y.H.Chen +3 位作者 G.J.Lyu K.K.Song J.M.Pelletier Y.Yao 《金属学报:英文版》 SCIE EI CAS CSCD 2019年第6期726-732,共7页
The dynamic mechanical relaxation behavior of Ti36.2Zr30.3Cu8.3Fe4Be21.2 bulk metallic glass with good glass-forming ability was investigated by mechanical spectroscopy.The mechanical relaxation behavior was analyzed ... The dynamic mechanical relaxation behavior of Ti36.2Zr30.3Cu8.3Fe4Be21.2 bulk metallic glass with good glass-forming ability was investigated by mechanical spectroscopy.The mechanical relaxation behavior was analyzed in the framework of quasi-point defects model.The experimental results demonstrate that the atomic mobility of the metallic glass is closely associated with the correlation factorχ.The physical aging below the glass transition temperature T g shows a non-Debye relaxation behavior,which could be well described by stretched Kohlrausch exponential equation.The Kohlrausch exponentβaging reflects the dynamic heterogeneities of the metallic glass.Both concentration of"defects"and atomic mobility decrease caused by the in situ successive heating during the mechanical spectroscopy experiments. 展开更多
关键词 Metallic GLASSES Mechanical RELAXATION Physical AGING Quasi-point defects
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