期刊文献+
共找到18,883篇文章
< 1 2 250 >
每页显示 20 50 100
ORBIT评分与HAS-BLED评分对心脏瓣膜置换术后华法林抗凝出血风险的预测价值比较
1
作者 赵慧明 刘勇 +3 位作者 粟丽 夏浩然 陈婷 王亚莉 《实用临床医药杂志》 CAS 2024年第6期83-87,共5页
目的比较ORBIT评分与HAS-BLED评分对心脏瓣膜置换术后华法林抗凝出血风险的预测价值。方法回顾性分析304例心脏瓣膜置换术后需行华法林抗凝治疗患者的病例资料,分别根据ORBIT评分和HAS-BLED评分对患者进行风险分层和分组,分析基于不同... 目的比较ORBIT评分与HAS-BLED评分对心脏瓣膜置换术后华法林抗凝出血风险的预测价值。方法回顾性分析304例心脏瓣膜置换术后需行华法林抗凝治疗患者的病例资料,分别根据ORBIT评分和HAS-BLED评分对患者进行风险分层和分组,分析基于不同评分的风险分层与术后华法林抗凝出血事件的相关性,比较2种评分方法风险分层的一致性及其对出血事件的预测价值。结果304例患者中,出血患者32例、未出血患者272例,出血患者的术后ORBIT评分、HAS-BLED评分均高于未出血患者,差异有统计学意义(P<0.05)。基于ORBIT评分划分的中危、高危患者的出血风险分别为低危患者的6.092(95%CI:2.694~13.775)倍、9.373(95%CI:1.465~59.943)倍,基于HAS-BLED评分划分的中危、高危患者的出血风险分别为低危患者的3.750(95%CI:1.383~10.166)倍、14.250(95%CI:5.489~36.995)倍。受试者工作特征曲线分析结果显示,ORBIT评分预测华法林抗凝出血风险的曲线下面积(AUC)为0.646(95%CI:0.589~0.699),敏感度为46.88%,特异度为87.87%,最佳截断值为3分;HAS-BLED评分预测华法林抗凝出血风险的AUC为0.768(95%CI:0.717~0.814),敏感度为75.00%,特异度为69.85%,最佳截断值为2分;Delong检验结果显示,2种评分的AUC差异有统计学意义(D=0.122,95%CI:0.001~0.245,Z=1.962,P<0.05)。结论ORBIT评分和HAS-BLED评分对心脏瓣膜置换术后华法林抗凝出血风险均具有一定预测价值,其中HAS-BLED评分的预测效能更优。 展开更多
关键词 心脏瓣膜置换术 华法林 抗凝 orbit评分 HAS-BLED评分 出血事件
下载PDF
Late infection after peri-orbital autologous micro-fat graft:a case presentation and literature review
2
作者 Farzad Pakdel Hassan Asadigandomani +5 位作者 Melika Arab Bafrani Zohreh Nozarian Zohre Abedinifar Niloofar Pirmarzdashti Behzad Jafari Zaynab Siami 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2024年第3期603-606,共4页
Citation:Pakdel F,Asadigandomani H,Arab Bafrani M,Nozarian Z,Abedinifar Z,Pirmarzdashti N,Jafari B,Siami Z.Late infection after peri-orbital autologous micro-fat graft:a case presentation and literature review.Int J O... Citation:Pakdel F,Asadigandomani H,Arab Bafrani M,Nozarian Z,Abedinifar Z,Pirmarzdashti N,Jafari B,Siami Z.Late infection after peri-orbital autologous micro-fat graft:a case presentation and literature review.Int J Ophthalmol 2024;17(3):603-606. 展开更多
关键词 GRAFT orbitAL AFTER
下载PDF
Theory for Charge Density Wave and Orbital-Flux State in Antiferromagnetic Kagome Metal FeGe
3
作者 马海洋 殷嘉鑫 +1 位作者 M.Zahid Hasan 刘健鹏 《Chinese Physics Letters》 SCIE EI CAS CSCD 2024年第4期90-104,共15页
We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe.Based on first-principles density functional theory calculations,we study the electronic str... We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe.Based on first-principles density functional theory calculations,we study the electronic structures,Fermi-surface quantum fluctuations,as well as phonon properties of the antiferromagnetic kagome metal FeGe.It is found that charge density wave emerges in such a system due to a subtle cooperation between electron-electron interactions and electron–phonon couplings,which gives rise to an unusual scenario of interaction-triggered phonon instabilities,and eventually yields a charge density wave(CDW)state.We further show that,in the CDW phase,the ground-state current density distribution exhibits an intriguing star-of-David pattern,leading to flux density modulation.The orbital fluxes(or current loops)in this system emerge as a result of the subtle interplay between magnetism,lattice geometries,charge order,and spin-orbit coupling(SOC),which can be described by a simple,yet universal,tight-binding theory including a Kane-Mele-type SOC term and a magnetic exchange interaction.We further study the origin of the peculiar step-edge states in FeGe,which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material. 展开更多
关键词 interaction PHONON orbitAL
下载PDF
Orbital-Ordering Driven Simultaneous Tunability of Magnetism and Electric Polarization in Strained Monolayer VCl_(3)
4
作者 郭的坪 王聪 +4 位作者 王侣锦 陆赟豪 吴骅 张妍宁 季威 《Chinese Physics Letters》 SCIE EI CAS CSCD 2024年第4期126-131,共6页
Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical pr... Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical predictions thus far have not ascertained whether monolayer VCl_(3) is a ferromagnetic(FM)or anti-FM monolayer;this also remains to be experimentally verified.We theoretically investigate the influence of potential factors,including C_(3) symmetry breaking,orbital ordering,epitaxial strain,and charge doping,on the magnetic ground state.Utilizing first-principles calculations,we predict a collinear type-Ⅲ FM ground state in monolayer VCl_(3) with a broken C_(3) symmetry,wherein only the former two of three t_(2g)orbitals(a_(1g),e_(g2)^(π)and e_(g1)^(π))are occupied.The atomic layer thickness and bond angles of monolayer VCl_(3) undergo abrupt changes driven by an orbital ordering switch,resulting in concomitant structural and magnetic phase transitions.Introducing doping to the underlying Cl atoms of monolayer VCl_(3) without C_(3) symmetry simultaneously induces in-and out-of-plane polarizations.This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain.The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl_(3). 展开更多
关键词 MONOLAYER symmetry orbitAL
下载PDF
Effect of navigation endoscopy combined with threedimensional printing technology in the treatment of orbital blowout fractures
5
作者 Jin-Hai Yu Yao-Hua Wang +3 位作者 Qi-Hua Xu Chao Xiong An-An Wang Hong-Fei Liao 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2024年第3期570-576,共7页
●AIM:To explore the combined application of surgical navigation nasal endoscopy(NNE)and three-dimensional printing technology(3DPT)for the adjunctive treatment of orbital blowout fractures(OBF).●METHODS:Retrospectiv... ●AIM:To explore the combined application of surgical navigation nasal endoscopy(NNE)and three-dimensional printing technology(3DPT)for the adjunctive treatment of orbital blowout fractures(OBF).●METHODS:Retrospective analysis was conducted on the data of patients with OBF who underwent surgical treatment at the Affiliated Eye Hospital of Nanchang University between July 2012 and November 2022.The control group consisted of patients who received traditional surgical treatment(n=43),while the new surgical group(n=52)consisted of patients who received NNE with 3DPT.The difference in therapeutic effects between the two groups was evaluated by comparing the duration of the operation,best corrected visual acuity(BCVA),enophthalmos difference,recovery rate of eye movement disorder,recovery rate of diplopia,and incidence of postoperative complications.●RESULTS:The study included 95 cases(95 eyes),with 63 men and 32 women.The patients’age ranged from 5 to 67y(35.21±15.75y).The new surgical group and the control group exhibited no statistically significant differences in the duration of the operation,BCVA and enophthalmos difference.The recovery rates of diplopia in the new surgical group were significantly higher than those in the control group at 1mo[OR=0.03,95%CI(0.01–0.15),P<0.0000]and 3mo[OR=0.11,95%CI(0.03–0.36),P<0.0000]postoperation.Additionally,the recovery rates of eye movement disorders at 1 and 3mo after surgery were OR=0.08,95%CI(0.03–0.24),P<0.0000;and OR=0.01,95%CI(0.00–0.18),P<0.0000.The incidence of postoperative complications was lower in the new surgical group compared to the control group[OR=4.86,95%CI(0.95–24.78),P<0.05].●CONCLUSION:The combination of NNE and 3DPT can shorten the recovery time of diplopia and eye movement disorder in patients with OBF. 展开更多
关键词 orbital blowout fracture three-dimensional printing ENDOSCOPY surgical navigation
下载PDF
Generation of orbital angular momentum hologram using a modified U-net
6
作者 郑志刚 韩菲菲 +1 位作者 王乐 赵生妹 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第3期401-407,共7页
Orbital angular momentum(OAM)holography has become a promising technique in information encryption,data storage and opto-electronic computing,owing to the infinite topological charge of one single OAM mode and the ort... Orbital angular momentum(OAM)holography has become a promising technique in information encryption,data storage and opto-electronic computing,owing to the infinite topological charge of one single OAM mode and the orthogonality of different OAM modes.In this paper,we propose a novel OAM hologram generation method based on a densely connected U-net(DCU),where the densely connected convolution blocks(DCB)replace the convolution blocks of the U-net.Importantly,the reconstruction process of the OAM hologram is integrated into DCU as its output layer,so as to eliminate the requirement to prepare training data for the OAM hologram,which is required by conventional neural networks through an iterative algorithm.The experimental and simulation results show that the OAM hologram can rapidly be generated with the well-trained DCU,and the reconstructed image's quality from the generated OAM hologram is significantly improved in comparison with those from the Gerchberg-Saxton generation method,the Gerchberg-Saxton based generation method and the U-net method.In addition,a 10-bit OAM multiplexing hologram scheme is numerically demonstrated to have a high capacity with OAM hologram. 展开更多
关键词 orbital angular momentum(OAM) HOLOGRAPHY OAM holography deep learning
下载PDF
Bessel–Gaussian beam-based orbital angular momentum holography
7
作者 季佳滢 郑志刚 +3 位作者 朱家龙 王乐 王新光 赵生妹 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期407-413,共7页
Orbital angular momentum(OAM), as a new degree of freedom, has recently been applied in holography technology.Due to the infinite helical mode index of OAM mode, a large number of holographic images can be reconstruct... Orbital angular momentum(OAM), as a new degree of freedom, has recently been applied in holography technology.Due to the infinite helical mode index of OAM mode, a large number of holographic images can be reconstructed from an OAM-multiplexing hologram. However, the traditional design of an OAM hologram is constrained by the helical mode index of the selected OAM mode, for a larger helical mode index OAM mode has a bigger sampling distance, and the crosstalk is produced for different sampling distances for different OAM modes. In this paper, we present the design of the OAM hologram based on a Bessel–Gaussian beam, which is non-diffractive and has a self-healing property during its propagation. The Fourier transform of the Bessel–Gaussian beam is the perfect vortex mode that has the fixed ring radius for different OAM modes. The results of simulation and experiment have demonstrated the feasibility of the generation of the OAM hologram with the Bessel–Gaussian beam. The quality of the reconstructed holographic image is increased, and the security is enhanced. Additionally, the anti-interference property is improved owing to its self-healing property of the Bessel-OAM holography. 展开更多
关键词 orbital angular momentum HOLOGRAPHY Bessel–Gaussian beam OAM-multiplexing hologram
下载PDF
d-d Orbital coupling induced by crystal-phase engineering assists acetonitrile electroreduction to ethylamine
8
作者 Honggang Huang Yao Chen +7 位作者 Hui Fu Cun Chen Hanjun Li Zhe Zhang Feili Lai Shuxing Bai Nan Zhang Tianxi Liu 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第2期216-225,I0006,共11页
The d-d orbital coupling induced by crystal-phase engineering can effectively adjust the electronic structure of electrocatalysts,thus showing significant catalytic performance,while it has been rarely explored in ele... The d-d orbital coupling induced by crystal-phase engineering can effectively adjust the electronic structure of electrocatalysts,thus showing significant catalytic performance,while it has been rarely explored in electrochemical acetonitrile reduction reaction(ARR)to date.Herein,we successfully realize the structural transformation of Pd Cu metallic aerogels(MAs)from face-centered cubic(FCC)to body-centered cubic(BCC)through annealing treatment.Specifically,the BCC Pd Cu MAs exhibit excellent ARR performance with high ethylamine selectivity of 90.91%,Faradaic efficiency of 88.60%,yield rate of 316.0 mmol h^(-1)g^(-1)_(Pd+Cu)and long-term stability for consecutive electrolysis within 20 h at-0.55 V vs.reversible hydrogen electrode,outperforming than those of FCC Pd Cu MAs.Under the membrane electrode assembly system,BCC Pd Cu MAs also demonstrate excellent ethylamine yield rate of 389.5 mmol h^(-1)g^(-1)_(Pd+Cu).Density functional theory calculation reveals that the d-d orbital coupling in BCC Pd Cu MAs results in an evident correlation effect for the interaction of Pd and Cu sites,which boosts up the Cu sites electronic activities to enhance ARR performance.Our work opens a new route to develop efficient ARR electrocatalysts from the perspective of crystalline structure transformation. 展开更多
关键词 d-d orbital coupling Crystal-phase engineering Metallic aerogels Acetonitrile electroreduction reaction ETHYLAMINE
下载PDF
Ab initio nonadiabatic molecular dynamics study on spin–orbit coupling induced spin dynamics in ferromagnetic metals
9
作者 朱万松 郑镇法 +1 位作者 郑奇靖 赵瑾 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期156-163,共8页
Understanding the photoexcitation induced spin dynamics in ferromagnetic metals is important for the design of photo-controlled ultrafast spintronic device.In this work,by the ab initio nonadiabatic molecular dynamics... Understanding the photoexcitation induced spin dynamics in ferromagnetic metals is important for the design of photo-controlled ultrafast spintronic device.In this work,by the ab initio nonadiabatic molecular dynamics simulation,we have studied the spin dynamics induced by spin–orbit coupling(SOC)in Co and Fe using both spin-diabatic and spin-adiabatic representations.In Co system,it is found that the Fermi surface(E_(F))is predominantly contributed by the spin-minority states.The SOC induced spin flip will occur for the photo-excited spin-majority electrons as they relax to the E_(F),and the spin-minority electrons tend to relax to the EFwith the same spin through the electron–phonon coupling(EPC).The reduction of spin-majority electrons and the increase of spin-minority electrons lead to demagnetization of Co within100 fs.By contrast,in Fe system,the E_(F) is dominated by the spin-majority states.In this case,the SOC induced spin flip occurs for the photo-excited spin-minority electrons,which leads to a magnetization enhancement.If we move the E_(F) of Fe to higher energy by 0.6eV,the E_(F) will be contributed by the spin-minority states and the demagnetization will be observed again.This work provides a new perspective for understanding the SOC induced spin dynamics mechanism in magnetic metal systems. 展开更多
关键词 nonadiabatic molecular dynamics spin dynamics spin–orbit coupling ferromagnetic metal
下载PDF
Asymmetric orbital hybridization in Zn-doped antiperovskite Cu_(1-x)Zn_(x)NMn_(3)enables highly efficient electrocatalytic hydrogen production
10
作者 Yuxiang Yan Yuxin Cao +9 位作者 Zhichao Wang Ka Wang Hengdong Ren Shaoqi Zhang Yi Wang Jian Chen Yong Zhou Lizhe Liu Jun Dai Xinglong Wu 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第2期304-312,I0008,共10页
Rational design of efficient and robust earth-abundant alkaline hydrogen evolution reaction(HER)catalysts is a key factor for developing energy conversion technologies.Currently,antiperovskite nitride CuNMn_(3)has gar... Rational design of efficient and robust earth-abundant alkaline hydrogen evolution reaction(HER)catalysts is a key factor for developing energy conversion technologies.Currently,antiperovskite nitride CuNMn_(3)has garnered significant interest due to its remarkable properties such as negative/zero thermal expansion and magnetocaloric effects.However,when utilized as hydrogen evolution catalysts,it encounters large challenge resulting from excessively strong/weak interactions with adsorbed H on Mn/Cu active sites,which leads to low HER activity.In this study,we introduce an asymmetric orbital hybridization strategy in Zn-doped Cu_(1-x)Zn_(x)NMn_(3)by leveraging the localization of Zn electronic states to reconfigure the electronic structures of Cu and Mn,thereby reducing the energy barrier for water dissociation and optimizing Cu and Mn active sites for hydrogen adsorption and H_(2)production.Electrochemical evaluations reveal that Cu_(0.85)Zn_(0.15)NMn_(3)with x=0.15 demonstrates exceptional electrocatalytic activity in alkaline electrolytes.A low overpotential of 52 mV at 10 mA cm^(-2)and outstanding stability over a 150-h test period are achieved,surpassing commercial Pt/C.This research offers a novel strategy for enhancing HER performance by modulating asymmetric hybridization of electron orbitals between multiple metal atoms within a material structure. 展开更多
关键词 Cu_(1-x)ZnxNMn_(3) Asymmetric orbital hybridization Hydrogen adsorption Hydrogen production
下载PDF
Fast solution to the free return orbit's reachable domain of the manned lunar mission by deep neural network
11
作者 YANG Luyi LI Haiyang +1 位作者 ZHANG Jin ZHU Yuehe 《Journal of Systems Engineering and Electronics》 SCIE CSCD 2024年第2期495-508,共14页
It is important to calculate the reachable domain(RD)of the manned lunar mission to evaluate whether a lunar landing site could be reached by the spacecraft. In this paper, the RD of free return orbits is quickly eval... It is important to calculate the reachable domain(RD)of the manned lunar mission to evaluate whether a lunar landing site could be reached by the spacecraft. In this paper, the RD of free return orbits is quickly evaluated and calculated via the classification and regression neural networks. An efficient databasegeneration method is developed for obtaining eight types of free return orbits and then the RD is defined by the orbit’s inclination and right ascension of ascending node(RAAN) at the perilune. A classify neural network and a regression network are trained respectively. The former is built for classifying the type of the RD, and the latter is built for calculating the inclination and RAAN of the RD. The simulation results show that two neural networks are well trained. The classification model has an accuracy of more than 99% and the mean square error of the regression model is less than 0.01°on the test set. Moreover, a serial strategy is proposed to combine the two surrogate models and a recognition tool is built to evaluate whether a lunar site could be reached. The proposed deep learning method shows the superiority in computation efficiency compared with the traditional double two-body model. 展开更多
关键词 manned lunar mission free return orbit reachable domain(RD) deep neural network computation efficiency
下载PDF
Robust measurement of orbital angular momentum of a partially coherent vortex beam under amplitude and phase perturbations
12
作者 Zhao Zhang Gaoyuan Li +5 位作者 Yonglei Liu Haiyun Wang Bernhard J.Hoenders Chunhao Liang Yangjian Cai Jun Zeng 《Opto-Electronic Science》 2024年第1期1-12,共12页
The ability to overcome the negative effects,induced by obstacles and turbulent atmosphere,is a core challenge of long-distance information transmission,and it is of great significance in free-space optical communicat... The ability to overcome the negative effects,induced by obstacles and turbulent atmosphere,is a core challenge of long-distance information transmission,and it is of great significance in free-space optical communication.The spatial-coherence structure,that characterizes partially coherent fields,provides a new degree of freedom for carrying information.However,due to the influence of the complex transmission environment,the spatial-coherence structure is severely damaged during the propagation path,which undoubtedly limits its ability to transmit information.Here,we realize the robust far-field orbital angular momentum(OAM)transmission and detection by modulating the spatial-coherence structure of a partially coherent vortex beam with the help of the cross-phase.The cross-phase enables the OAM information,quantified by the topological charge,hidden in the spatial-coherence structure can be stably transmitted to the far field and can resist the influence of obstructions and turbulence within the communication link.This is due to the self-reconstruction property of the spatial-coherence structure embedded with the cross-phase.We demonstrate experimentally that the topological charge information can be recognized well by measuring the spatial-coherence structure in the far field,exhibiting a set of distinct and separated dark rings even under amplitude and phase perturbations.Our findings open a door for robust optical signal transmission through the complex environment and may find application in optical communication through a turbulent atmosphere. 展开更多
关键词 degree of coherence orbital angular momentum cross-phase topological charge information transmission
下载PDF
FAO下信号系统与站台门一体化方案 被引量:1
13
作者 崔惠珊 盖克荣 +1 位作者 李雪枝 刘伊敏 《铁路通信信号工程技术》 2023年第5期62-66,共5页
全自动运行系统对站台门提出新的功能需求和安全需求,灵活编组、车-车通信进一步增加对站台门的可靠性及可用性的要求,信号系统与站台门一体化的概念被提出和逐渐清晰。分析现有站台门系统的问题和工程实践中一体化的方案和特点,提出车... 全自动运行系统对站台门提出新的功能需求和安全需求,灵活编组、车-车通信进一步增加对站台门的可靠性及可用性的要求,信号系统与站台门一体化的概念被提出和逐渐清晰。分析现有站台门系统的问题和工程实践中一体化的方案和特点,提出车-车通信下信号系统与站台门一体化设计方案:基于对象控制器的中央控制盘一体化设计和对象控制器OC直接控制门控器的一体化设计方案,并对比两种方案的实施效果。 展开更多
关键词 全自动运行系统 对象控制器 站台门 一体化设计
下载PDF
FAO系统下列车火灾应急处置GSPN模型与分析
14
作者 李艳艳 张孝法 《山东交通学院学报》 CAS 2023年第3期63-71,80,共10页
为提高轨道交通全自动运行(fully automatic operation,FAO)状态下无人值守地铁列车突发火灾应急处置效率和应急管理水平,分析FAO系统下地铁列车区间火灾的应急处置流程,基于广义随机Petri网(generalized stochastic Petri net,GSPN)建... 为提高轨道交通全自动运行(fully automatic operation,FAO)状态下无人值守地铁列车突发火灾应急处置效率和应急管理水平,分析FAO系统下地铁列车区间火灾的应急处置流程,基于广义随机Petri网(generalized stochastic Petri net,GSPN)建立FAO系统下无人值守列车的火灾应急处置的GSPN模型及其同构的马尔科夫链(Markov chain,MC);结合地铁列车火灾应急演练操作流程进行实证仿真,分析应急处置流程模型的系统性能,确定关键环节及其处置时间。结果表明:在救援行动阶段,救援人员行动、乘客到达安全车厢、列车到站、车站处置完成和救援行动完成等环节易造成信息堵塞;开展车站处置、车站救援和事故列车下线等环节的变迁利用率相对较高,为应急处置流程优化的重点;通过变动关键环节的变迁实施速率,仿真系统的平衡状态与应急处置效率间的关系,确定关键环节的最佳变迁实施速率及应急处置总时长,为FAO系统下优化列车火灾应急处置流程提供参考。 展开更多
关键词 fao系统 列车火灾 应急处置 GSPN MC
下载PDF
基于1961-2020年FAO数据的世界高粱产业分析 被引量:5
15
作者 邹剑秋 《山西农业大学学报(自然科学版)》 CAS 北大核心 2023年第1期1-10,共10页
[目的]高粱是世界第五大禾谷类作物,作为高光效C4作物具有抗旱、耐涝、耐盐碱、耐瘠薄等多重抗性,在保证全球粮食安全及促进边际土地利用方面发挥着不可替代的关键作用。[方法]本文以1961-2020年FAO数据为基础,结合海关等数据对世界高... [目的]高粱是世界第五大禾谷类作物,作为高光效C4作物具有抗旱、耐涝、耐盐碱、耐瘠薄等多重抗性,在保证全球粮食安全及促进边际土地利用方面发挥着不可替代的关键作用。[方法]本文以1961-2020年FAO数据为基础,结合海关等数据对世界高粱的分布、面积、总产量、单位面积产量、我国产业现状及进出口情况等进行了分析与探讨。[结果]分析发现,1961-2020年世界高粱年平均收获面积非洲>亚洲>美洲>大洋洲>欧洲,亚洲、非洲、美洲3大高粱主要生产洲非洲增加、亚洲下降、美洲平稳,总产量美洲>非洲>亚洲>大洋洲>欧洲,而单位面积产量欧洲、美洲和大洋洲高于世界平均水平,亚洲和非洲相对较低;2020年世界高粱主产国中高粱收获面积苏丹、印度、尼日利亚、尼日尔产量排在前列,总产美国>尼日利亚>埃塞俄比亚>印度>墨西哥>中国>巴西>苏丹>其他国家,美国总产量最高,为947.4万t;我国高粱收获面积排名第12,总产量排名第6,单位面积产量排名第2;内蒙古、吉林、贵州、黑龙江、辽宁、四川、山西、河南等省区为高粱主要产区;目前,我国是高粱进口大国,总体进口数量持续增加。[结论]世界高粱产业稳步发展,面积、总产量、单位面积产量等变化具有规律性和必然性,高粱生产不断向更为干旱瘠薄的非洲转移。中国作为高粱重要主产国在世界高粱产业格局中发挥着重要作用,应进一步加强相关研究与应用,调整优化产业政策,挖掘提高干旱、盐碱、瘠薄土壤高粱生产能力,满足市场的多样化需求。 展开更多
关键词 fao 世界 中国 高粱 产业
下载PDF
Difference of anterior and posterior orbital development in patients with congenital microphthalmia:a retrospective cohort study from China 被引量:1
16
作者 Ju Zhang Zhi-Jia Hou +2 位作者 Jun-Fang Xian Qing-Lin Chang Dong-Mei Li 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2023年第3期411-417,共7页
AIM:To evaluate volume differences between anterior and posterior orbit and demographic characteristics of Chinese patients with congenital microphthalmia.METHODS:A retrospective cohort study,involving 169 unilateral ... AIM:To evaluate volume differences between anterior and posterior orbit and demographic characteristics of Chinese patients with congenital microphthalmia.METHODS:A retrospective cohort study,involving 169 unilateral congenital microphthalmia patients aged between 1 and 57 years old was conducted.Three-dimensional images of the orbit were generated from past CT scans,and digital orbital volume comprehensive measurement was done.The measured data included orbital volume(OBV),posterior orbital volume(POV),orbital width(OBW),orbital height(OBH),orbital depth(OBD),and posterior orbital area ratio.RESULTS:Significant differences were observed among OBV,POV,OBW,OBH,and OBD of the affected and unaffected eyes in different age-based groups(all P<0.001).Among them,OBH had the greatest different.The mean microphthalmic to contralateral ratio(MCR) of OBV,POV,OBW,and OBH continuously increased from 1 to 3 years old,whereas the MCR of POV decreased from 3 to 17 years old.The MCR of OBD was not found to be correlated to age.There was no significant difference between OBV,POV,OBW,and OBH in ages from 13 years old to adulthood(all P>0.05).The difference in posterior orbital area ratio between the affected and unaffected groups was not statistically significant(P>0.05).CONCLUSION:OBH is maximally affected,whereas OBD is minimally affected by microphthalmia.Posterior orbital retardation began 2y prior to orbital retardation and occurred at 3 years old in the affected eye,suggesting that intervention therapy should be done before the age of 4. 展开更多
关键词 orbital measurement congenital microphthalmia tomography spiral computed
下载PDF
Asymmetrical spiral spectra and orbital angular momentum density of non-uniformly polarized vortex beams in uniaxial crystals 被引量:1
17
作者 舒凌云 程科 +2 位作者 廖赛 梁梦婷 杨嶒浩 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第2期323-331,共9页
To explore the effect of non-uniform polarization on orbital angular momentum(OAM) in anisotropic medium, in this work investigated are the evolution of the spiral spectra and OAM densities of non-uniformly polarized ... To explore the effect of non-uniform polarization on orbital angular momentum(OAM) in anisotropic medium, in this work investigated are the evolution of the spiral spectra and OAM densities of non-uniformly polarized vortex(NUPV)beams in uniaxial crystals propagating orthogonal to the optical axis, and also the case of uniformly polarized vortex(UPV)beams with left-handed elliptical polarization. In the input plane, the NUPV beams present their spiral spectra of m-mode concentrated at m = l ± 1 modes rather than m = l mode, and reveal the relation among topological charge l, mode of spiral spectra m and the power weight value Rmexpressed by l=∑^(∞)_(m)=-∞Rm. is still satisfied for UPV beams in uniaxially anisotropic crystals, whereas for NUPV beams their relations are no longer valid owing to non-uniform polarization. Furthermore, the analysis indicates that the asymmetrical distribution of power weight of spiral spectra and the non-zero value in the sum of longitudinal OAM densities originate from the initial non-uniform polarization and anisotropy in uniaxial crystals rather than topological charges. In addition, the relation between spiral spectrum and longitudinal OAM density is numerically discussed. This work may provide an avenue for OAM-based communications,optical metrology, and imaging by varying the initial non-uniform polarization. 展开更多
关键词 non-uniformly polarized beams spiral spectrum spin angular momentum orbital angular momentum VORTEX
下载PDF
FAO-PM法估算季节性冰冻地区路基土潜在蒸发蒸腾量
18
作者 李冬雪 孙宗元 李聪 《重庆交通大学学报(自然科学版)》 CAS CSCD 北大核心 2023年第4期62-70,86,共10页
为准确估算东北东部山地润湿冻区(Ⅱ_(1)区)路基土平衡湿度,引入联合国粮农组织Penman-Monteith法(FAO-PM)估算气候因素控制型路基土潜在蒸发蒸腾量,以解决Thornthwaite法在负温时潜在蒸发蒸腾量计算值为0的问题。详细阐述了FAO-PM模型... 为准确估算东北东部山地润湿冻区(Ⅱ_(1)区)路基土平衡湿度,引入联合国粮农组织Penman-Monteith法(FAO-PM)估算气候因素控制型路基土潜在蒸发蒸腾量,以解决Thornthwaite法在负温时潜在蒸发蒸腾量计算值为0的问题。详细阐述了FAO-PM模型中5个气候因素的具体含义,并给出算例说明计算流程;根据Ⅱ_(1)区内6个气象台站月均气象数据计算得到各地路基土潜在蒸发蒸腾量;分析主要气候因素对路基土潜在蒸发蒸腾量的影响规律与程度。研究表明:Ⅱ_(1)区各地路基土全年潜在蒸发蒸腾总量为71.14~87.37 cm,负温时该值为8.27~12.39 cm,占全年总量的9.8%~15.7%;潜在蒸发蒸腾量与各地平均气温的显著正相关关系可在一定程度上削弱与其他气候因素的负相关关系;负温条件下,路基的潜在蒸发蒸腾量与平均气温、平均风速和平均日照时数呈正比,与平均相对湿度呈反比;FAO-PM法估算的逐月潜在蒸发蒸腾量与气象站实测数据的误差范围为0.47~13.22 cm,负温时误差范围为0.47~4.31 cm。因此,FAO-PM法适用于估算公路自然区划Ⅱ_(1)区路基土潜在蒸发蒸腾量,且具有可接受的估算误差。 展开更多
关键词 道路工程 潜在蒸发蒸腾量 fao-PM法 路基 山地润湿冻区(Ⅱ_(1)区)
下载PDF
国际粮农动态:常驻联合国粮农机构大使会见FAO驻华代表等3则 被引量:1
19
作者 郭粟 李建民 黄飞 《世界农业》 2023年第1期131-132,共2页
常驻联合国粮农机构大使会见FAO驻华代表当地时间2022年12月13日上午,中国常驻联合国粮农机构代表、大使广德福在罗马应约会见联合国粮食农组织(FAO)驻华代表文康农,就加强中国与FAO务实合作交换意见。广德福表示,中国经济总量虽然已跻... 常驻联合国粮农机构大使会见FAO驻华代表当地时间2022年12月13日上午,中国常驻联合国粮农机构代表、大使广德福在罗马应约会见联合国粮食农组织(FAO)驻华代表文康农,就加强中国与FAO务实合作交换意见。广德福表示,中国经济总量虽然已跻身世界第二位,但人均GDP仅居全球第66位,中国作为最大的发展中国家的定位没有改变。 展开更多
关键词 联合国粮农机构 fao 人均GDP 务实合作 中国经济总量 发展中国家 广德
下载PDF
Orbital liposarcoma: a retrospective, single-center study of thirteen patients
20
作者 Ning Gao Xin Ge +2 位作者 Cheng Pei Jian-Min Ma Ya-Guang Hu 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2023年第8期1293-1298,共6页
AIM:To explore the clinical and pathological characteristics of thirteen patients with orbital liposarcoma.METHODS:The clinical history data of thirteen patients diagnosed as orbital liposarcoma at Beijing Tongren Hos... AIM:To explore the clinical and pathological characteristics of thirteen patients with orbital liposarcoma.METHODS:The clinical history data of thirteen patients diagnosed as orbital liposarcoma at Beijing Tongren Hospital,from 2006 to 2021 were collected and analyzed.The data includes age,gender,affected orbital side,course of disease,status of disease(primary or recurrent),clinical manifestations,preoperative visual acuity,operative treatment,the relations between liposarcoma and surrounding tissue,longest diameter of liposarcoma,histological subtype,immunohistochemical indicators,follow-up treatment and prognosis.RESULTS:The initial symptoms are diverse.Proptosis is the most frequent chief complaint and the others included vision loss,epiphora,diplopia,and eyelid palpable mass.Results of imaging examination[computed tomography(CT)or magnetic resonance imaging(MRI)]showed orbital mass.In terms of treatment,10 patients received tumor resection,and the mean longest diameter of the tumor was 3.39±1.36 cm.The other 3 patients had optic nerve invaded,so they received orbital exenteration.Pathological examination results confirmed the diagnose of liposarcoma for 13 patients.Six patients displayed as myxoid type,and three patients in each type of dedifferentiated and welldifferentiated type.One patient was verified as pleomorphic,which was a rare type of liposarcoma.All of the patients showed Vimentin positive,and most showed CD34 and S-100 positive.Besides,four patients showed smooth muscle actin positive.All thirteen patients were alive.CONCLUSION:Orbital liposarcoma is a rare disease and it has no specific clinical manifestation.The diagnosis of liposarcoma should be considered when proptosis and orbital mass occurred in orbit.It is recommended to perform pathological examination to achieve early detection and early treatment. 展开更多
关键词 LIPOSARCOMA orbital tumor orbital mass PROPTOSIS
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部