期刊文献+
共找到1,629篇文章
< 1 2 82 >
每页显示 20 50 100
Performance evaluations on inner vs. outer decomposition first parallel join algorithms for two nested loop joins
1
作者 Seo-Young NOH Heejun YOON +2 位作者 Il-Yeon YEO Yoon-su JEONG Hyungwoo PARK 《Journal of Central South University》 SCIE EI CAS 2014年第10期3873-3882,共10页
Two popular traditional join algorithms and their parallel versions are introduced. When designing join algorithms in serial computing environment, decomposing inner relation is considered as the right direction to sa... Two popular traditional join algorithms and their parallel versions are introduced. When designing join algorithms in serial computing environment, decomposing inner relation is considered as the right direction to save disk I/Os. However, two different decomposition algorithms are compared, such as inner vs. outer decomposition first algorithms for tuple-based and block-based nested loop joins, showing that the proposed approach is 20% better than general approach. Also lemmas are proved, when we have to use the outer decomposition first parallel join algorithms. 展开更多
关键词 parallel join performance inner decomposition outer decomposition
在线阅读 下载PDF
DS-CDMA system outer loop power control and improvement for multi-service 被引量:3
2
作者 Guan Mingxiang Guo Qing Li Xing 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2008年第3期453-460,共8页
When a new user accesses the CDMA system, the load will change drastically, and therefore, the advanced outer loop power control (OLPC) technology has to be adopted to enrich the target signal interference ratio (S... When a new user accesses the CDMA system, the load will change drastically, and therefore, the advanced outer loop power control (OLPC) technology has to be adopted to enrich the target signal interference ratio (Silt) and improve the system performance. The existing problems about DS-CDMA outer loop power control for multi-service are introduced and the power control theoretical model is analyzed. System simulation is adopted on how to obtain the theoretical performance and parameter optimization of the power control algorithm. The OLPC algorithm is improved and the performance comparisons between the old algorithm and the improved algorithm are given. The results show good performance of the improved OLPC algorithm and prove the validity of the improved method for multi-service. 展开更多
关键词 DS-CDMA outer loop power control MULTI-SERVICE performance.
在线阅读 下载PDF
Transformations of phosphatidylinositol phosphates in the outer and inner nuclear membrane are linked to synthesis and restitution of cellular membranes 被引量:5
3
作者 Amalia Slomiany Bronislaw L. Slomiany 《Health》 2011年第4期187-199,共13页
The ultimate goal in phosphoinositides cellular metabolism is to decipher their global functional organization and coordination of the com- partmentalized signaling processes. In this report we present evidence linkin... The ultimate goal in phosphoinositides cellular metabolism is to decipher their global functional organization and coordination of the com- partmentalized signaling processes. In this report we present evidence linking nuclear phos- phoinositides cycle with endoplasmic reticulum synthesis and function. The rapid transformation of [3H]inositol-labeled phosphoinositides in the intact nuclei (IN) was captured in chase studies for 0-5 min, followed by examination of phosphatidylinositides in the inner nuclear me- mbrane (INM), the outer nuclear membrane (ONM) and endoplasmic reticulum (ER). We revealed that synthesis of phosphatidylinositol phosphates (PIPs) occurs in ONM and the de- phosphorylation takes place in the INM. The rapid transformation of the radiolabeled PIPs in ONM reverberated in their appearance and successive transformation in INM, and in the 5min chased nuclei was tracked to ONM as the re- emerging radiolabeled phosphatidylinositol (PI). These chase-uncovered changes in ONM and INM PIPs profiles allow us to conclude that the observed conversions in the nuclear membrane continuum are induced by the lateral movement of the membrane and its transit from the cytosolic to nuclear and back to cytosolic environment. The suggested membrane synthesisinduced movement provides the means to transport the membrane- and the membrane lipid ligand-associated cytosolic proteins to the intranuclear spaces and renewal of INM. Export of the nuclear components interacting with the modified INM, by exiting from nuclear to cytosolic site, endows ER with a steady influx of the membrane that is conditioned to generate vesicles according to the nucleus delivered templates. 展开更多
关键词 Phosphatidylinositides PIPs Transformation RESTITUTION outer NUCLEAR MEMBRANE inner NUCLEAR MEMBRANE Endoplasmic Reticulum CELLULAR Membranes
暂未订购
Lipophilic extractives of the inner and outer barks from six different Pinus species grown in Indonesia 被引量:2
4
作者 Masendra Tatsuya Ashitani +1 位作者 Koetsu Takahashi Ganis Lukmandaru 《Journal of Forestry Research》 SCIE CAS CSCD 2018年第5期1329-1336,共8页
The chemical compositions of the dichloromethane extracts of inner and outer barks from six Pinus species(P.elliotii,P.oocarpa,P.caribeae,P.merkusii,P.montezumae,and P.insularis) grown in Indonesia were investigated... The chemical compositions of the dichloromethane extracts of inner and outer barks from six Pinus species(P.elliotii,P.oocarpa,P.caribeae,P.merkusii,P.montezumae,and P.insularis) grown in Indonesia were investigated by GC and GC–MS.Generally,the amounts of extractive contents were higher in the inner bark than in the outer bark except for P.merksuii.Fatty acids,monoterpenes,sesquiterpenes,resin acids,triterpenoids,and steroids were detected and quantified.Inner and outer barks differed not only in content of these compounds but also in their composition.Fatty acids and alcohols were the major classes of lipophilic compounds in the outer bark of P.caribeae, P.insularis,and P.montezumae.Steroids and triterpenoids were the dominant compounds identified in the inner bark of P.elliotii,P.insularis,and P.merkusii.Resin acids were the most abundant group in the inner bark of P.oocarpa whereas monoterpenes and sesquiterpenes were recorded in minor quantities in both bark layers of all species. 展开更多
关键词 Bark extractive LIPOPHILIC inner bark outer bark Pinus spp
在线阅读 下载PDF
Viscous Inner and Outer Pressure Forming Method of Thin-walled Tube and Its Application 被引量:3
5
作者 高铁军 LIU Yang WANG Zhongjin 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2015年第2期404-407,共4页
Aiming at overcoming the difficulties in integral forming of thin-walled tubes with complex shapes, a novel forming method by inner and outer pressure through viscous was proposed. In this method, by dividing large de... Aiming at overcoming the difficulties in integral forming of thin-walled tubes with complex shapes, a novel forming method by inner and outer pressure through viscous was proposed. In this method, by dividing large deformation of the part into inner and outer pressure forming deformations, the limit deformation of tube part can be increased by several times. Meanwhile, the principle of viscous inner and outer pressure forming was provided, and key problems during the forming process such as reduction of the wall-thickness and instability wrinkling were analyzed. Thereby, the complex curved surface super-alloy GH3044 thin-walled tube with varying diameter ratio of 1.35(the ratio between the maximum and minimum diameters of the part) can be integrally formed by this method. The experimental surface of the formed part is superior in quality and the wall-thickness distribution is uniform. The results show that the viscous inner and outer pressure forming can provide a new approach for integral forming of thin-walled tubes with complex shapes. 展开更多
关键词 thin-walled tube inner and outer pressure forming viscous medium integral forming
原文传递
Influence of Inner/Outer Stator Pole Ratio and Relative Position on Electromagnetic Performance of Partitioned Stator Switched Flux Permanent Magnet Machines 被引量:1
6
作者 J.T.Shi Z.Q.Zhu 《CES Transactions on Electrical Machines and Systems》 CSCD 2019年第3期259-268,共10页
Based on the 6-pole outer stator(armature winding-stator),the influence of inner(permanent magnet-stator)/outer stator pole ratio n(n=NIS/NOS),stator relative positions and rotor pole number combinations on electromag... Based on the 6-pole outer stator(armature winding-stator),the influence of inner(permanent magnet-stator)/outer stator pole ratio n(n=NIS/NOS),stator relative positions and rotor pole number combinations on electromagnetic performance of partitioned stator switched flux permanent magnet(PM)machines(PS-SFPMMs)is investigated in this paper.Since the armature windings and PMs are located in two separated stators and PMs are stationary,PS-SFPMMs have high fault tolerance capabilities.To maximize the torque performance,the PM of inner stator pole should be aligned with outer stator pole when n is odd while the iron rib of inner stator pole should be aligned with outer stator pole when n is even.No matter what n is selected,the rotor pole number NR can be any integers except the phase number and its multiples.The analysis results indicate that the optimal NR is closed to(NIS+NOS)/2 and it is odd when n is odd while it is even when n is even.Meanwhile,symmetrical phase back-EMF waveform will be obtained when the ratio of Min(NOS,NIS)to the greatest common divisor of Min(NOS,NIS)and NR is even.Based on the optimal rotor pole numbers for 6-pole outer stator with different n and corresponding optimal relative position together with same rated copper loss,the average torque is improved by 18.4%,25.1%and 25.7%respectively in PS-SFPMMs with n equal to 2,3 and 4 when compared with PS-SFPMM with n equal to 1.The analyses are validated by experiment results of the prototype machine. 展开更多
关键词 inner/outer stator partitioned stator permanent magnet pole ratio relative position switched flux.
在线阅读 下载PDF
Inner and outer pressure forming of nickel based super-alloy thin-walled part with variable diameter sections 被引量:3
7
作者 王忠金 高铁军 《中国有色金属学会会刊:英文版》 EI CSCD 2008年第2期285-290,共6页
A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room tempera... A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature,and the principle of the method was provided.Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio(35%).The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet.The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections.The thinning of wall-thickness is less than 4%.This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections. 展开更多
关键词 压力成型技术 合金 直径 变量
在线阅读 下载PDF
Outer Loop Power Control Algorithm Based on T-norms Information Fusion Technology in TD-SCDMA
8
作者 孙毅 李芹 唐良瑞 《China Communications》 SCIE CSCD 2011年第3期180-188,共9页
An outer loop power control algorithm based on triangle norm(t-norm) information fusion technology is proposed in this paper.According to the difference between block error rate and bit error rate with target values,t... An outer loop power control algorithm based on triangle norm(t-norm) information fusion technology is proposed in this paper.According to the difference between block error rate and bit error rate with target values,the membership function calculation and level dividing of the two differences are dealt with.And then t-norm operator is used to fuse the two membership function values to determine the adjustment step-size.The algorithm can acquire the optimal adjustment step-size in the light of the channel status and avoid the overshoot phenomenon of the existing outer power control methods.As a result,the block error rate can converge to the target value quickly.Experiment results verify the excellent property of the algorithm. 展开更多
关键词 outer loop power control BLER t-norm operator information fusion TD-SCDMA
在线阅读 下载PDF
Synchronization investigation of the network group constituted by the nearest neighbor networks under inner and outer synchronous couplings
9
作者 李亭亭 李成仁 +4 位作者 王晨 何芳君 周光冶 孙景昌 韩非 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第12期572-576,共5页
A new synchronization technique of inner and outer couplings is proposed in this work to investigate the synchro- nization of network group. Some Haken-Lorenz lasers with chaos behaviors are taken as the nodes to cons... A new synchronization technique of inner and outer couplings is proposed in this work to investigate the synchro- nization of network group. Some Haken-Lorenz lasers with chaos behaviors are taken as the nodes to construct a few nearest neighbor complex networks and those sub-networks are also connected to form a network group. The effective node controllers are designed based on Lyapunov function and the complete synchronization among the sub-networks is realized perfectly under inner and outer couplings. The work is of potential applications in the cooperation output of lasers and the communication network. 展开更多
关键词 synchronization of network group inner and outer couplings Haken-Lorenz laser nearest neigh-bor network
原文传递
Forward masking in distinguishing inner and outer hair cell damage
10
作者 DUAN Mao-li Department of Clinical Neuroscience,Karolinska Institutet Department of Otorhinolaryngology Head and Neck & Center for Hearing and Communication Research,Karolinska University Hospital,Sweden 《Journal of Otology》 2009年第1期23-25,共3页
Forward Masking Temporal audiotory resolution is the ability of the auditory system to resolve auditory signals in the time domain. Forward masking is a means of studying temporal resolution where one tone, the probe,... Forward Masking Temporal audiotory resolution is the ability of the auditory system to resolve auditory signals in the time domain. Forward masking is a means of studying temporal resolution where one tone, the probe, is masked by a preceding tone, the masker. Forward masking is 展开更多
关键词 CELL Forward masking in distinguishing inner and outer hair cell damage ABR
暂未订购
Sanitary Sewage Treatment with Jet Inner-loop Bioreactor
11
作者 WenQin-xue ChenZhi-qiang +1 位作者 LuBing-nan WenYan 《Wuhan University Journal of Natural Sciences》 EI CAS 2004年第3期388-394,共7页
A jet inner-loop bioreactor (JIBR) was used to treat synthetic sanitary sewage with low, medium and high COD load. The experimental results show that it could meet discharge standard at 20\|30 min of HRT (hydraulic re... A jet inner-loop bioreactor (JIBR) was used to treat synthetic sanitary sewage with low, medium and high COD load. The experimental results show that it could meet discharge standard at 20\|30 min of HRT (hydraulic retention time) for low COD concentration and 60\|120 min of HRT for medium and high COD concentration. The maximal COD volume loading and COD sludge loading of 27 kg\5m -3 \5d -1 and 5 kg/d per kg MLSS were acheived respectively, that were 10\|20 times higher than those of traditional wastewater treatment processes. The BOD 5 removal efficiency was more than 90% and NH + 4 —N more than 85%. The study on the activity showed that the oxygen consumption rate of the activated sludge in the JIBR was 39.13 mg\5L -1 \5h -1 , which was 1.7 times higher than that of the SBR(Sequencing Batch Reactor) and the dominant bacteria in jet inner\|loop bioreactor was Pseudomonas species. 展开更多
关键词 jet inner-loop bioreactor sanitary sewage volume loading sludge loading
在线阅读 下载PDF
On the System-Level Analysis of Outer Loop Link Adaptation for IEEE 802,16e Systems
12
作者 Andre M. Cavalcante Edgar B. Sotlza +3 位作者 Juliano J. Bazzo Marco J. Souza Lauri Kuru Jani Moilanen 《通讯和计算机(中英文版)》 2012年第5期568-575,共8页
关键词 无线通信系统 链路自适应 IEEE 级分 外环 高速下行分组接入 标准化委员会 HSDPA
在线阅读 下载PDF
Structural insights into Deinococcus radiodurans BamA:extracellular loop diversity and its evolutionary implications
13
作者 Zhenzhou Wang Jinchan Xue +3 位作者 Jiajia Wang Jiangliu Yu Hongwu Qian Xinxing Yang 《中国科学技术大学学报》 CAS CSCD 北大核心 2024年第9期34-43,69,共11页
Diderm bacteria,characterized by an additional lipid membrane layer known as the outer membrane,fold their outer membrane proteins(OMPs)via theβ-barrel assembly machinery(BAM)complex.Understanding how the BAM complex... Diderm bacteria,characterized by an additional lipid membrane layer known as the outer membrane,fold their outer membrane proteins(OMPs)via theβ-barrel assembly machinery(BAM)complex.Understanding how the BAM complex,particularly its key component BamA,assists in OMP folding remains crucial in bacterial cell biology.Recent research has focused primarily on the structural and functional characteristics of BamA within the Gracilicutes clade,such as in Escherichia coli(E.coli).However,another major evolutionary branch,Terrabacteria,has received comparatively less attention.An example of a Terrabacteria is Deinococcus radiodurans(D.radiodurans),a Gram-positive bacterium that possesses a distinctive outer membrane structure.In this study,we first demonstrated that theβ-barrel domains of BamA are not interchangeable between D.radiodurans and E.coli.The structure of D.radiodurans BamA was subsequently determined at 3.8Åresolution using cryo-electron microscopy,revealing obviously distinct arrangements of extracellular loop 4(ECL4)and ECL6 after structural comparison with their counterparts in gracilicutes.Despite the overall similarity in the topology of theβ-barrel domain,our results indicate that certain ECLs have evolved into distinct structures between the Terrabacteria and Gracilicutes clades.While BamA and its function are generally conserved across diderm bacterial species,our findings underscore the evolutionary diversity of this core OMP folder among bacteria,offering new insights into bacterial physiology and evolutionary biology. 展开更多
关键词 BamA extracellular loop outer membrane protein Deinococcus radiodurans
在线阅读 下载PDF
同步密封壳内外壁圆环凹槽复合脱模机构注塑模设计 被引量:2
14
作者 张利华 《中国塑料》 北大核心 2025年第2期94-99,共6页
为同步密封壳塑件的注塑成型创新设计了一副多板式一模两腔潜伏式浇口两板模,采用分区分步进行脱模来实现塑件的自动化注塑生产。具体做法为:现将内壁的整圈圆环凹槽分解成4段,其中2段使用内收滑块实施抽芯脱模,剩余2段则使用2个“瓦片... 为同步密封壳塑件的注塑成型创新设计了一副多板式一模两腔潜伏式浇口两板模,采用分区分步进行脱模来实现塑件的自动化注塑生产。具体做法为:现将内壁的整圈圆环凹槽分解成4段,其中2段使用内收滑块实施抽芯脱模,剩余2段则使用2个“瓦片”形斜顶实施侧抽芯脱模,而外壁上的半圆环凹槽则使用2个定模侧哈夫滑块实施侧抽芯脱模,塑件最终由推板推出脱模。塑件的完全脱模由模具的5个动作来实现,包括3次开模动作和2次推出动作,其中第3次开模与2次顶出为同步动作。第1次开模使内收滑块实现内壁圆环凹槽的部分脱模,紧接着使外壁的哈夫滑块完成侧抽芯脱模,第2次为塑件从型腔镶件中脱出,第3次开模动作中,同时也包含2次顶出机构的2次顶出动作。第1次顶出为内壁剩余圆环凹槽使用2次顶出机构的1次顶出板推动斜顶顶出而实现,第2次为上推板将塑件从芯部成型件上推出而实现完全脱模。 展开更多
关键词 同步密封壳 外壁圆环凹槽 内壁圆环凹槽 哈夫滑块 内收滑块 斜顶 二次顶出
在线阅读 下载PDF
基于起裂荷载确定软岩抗拉强度的试验验证
15
作者 马春德 谭观霜 +2 位作者 张俊杰 赵俊康 阳文源 《中南大学学报(自然科学版)》 北大核心 2025年第4期1397-1404,共8页
针对圆环劈裂试验中基于峰值荷载导致岩石抗拉强度被高估的缺陷,对不同内外径比(0.2、0.3、0.4、0.5、0.6)的红砂岩圆环试样进行劈裂试验,利用3种手段(声发射、应变片及数字图像相关技术)捕捉拉伸裂纹起裂点,以期提高圆环劈裂试验测试... 针对圆环劈裂试验中基于峰值荷载导致岩石抗拉强度被高估的缺陷,对不同内外径比(0.2、0.3、0.4、0.5、0.6)的红砂岩圆环试样进行劈裂试验,利用3种手段(声发射、应变片及数字图像相关技术)捕捉拉伸裂纹起裂点,以期提高圆环劈裂试验测试岩石抗拉强度的准确性。同时,对红砂岩进行巴西劈裂及直接拉伸试验,验证圆环劈裂试验结果的准确性。研究结果表明:圆环起裂荷载随着内外径比增大而降低,当内外径比为0.5和0.6时,基于起裂荷载计算得到的抗拉强度接近直接拉伸强度(相对偏差最小仅为3.3%)。基于起裂点的圆环劈裂试验是测试软岩间接抗拉强度的可靠方法。 展开更多
关键词 抗拉强度 圆环劈裂试验 起裂荷载 内外径比
在线阅读 下载PDF
多边界约束的无线电能传输内外双层线圈设计研究
16
作者 廖志凌 管建鹏 +1 位作者 王华佳 陈兆岭 《电力电子技术》 2025年第12期143-149,共7页
无线电能传输(WPT)系统谐振网络的参数设计对于电能安全高效传输至关重要。在满足系统多约束条件下实施谐振线圈的优化设计是一种十分实用且高效快速的方法。然而,传统的单层线圈绕制方案无法满足多约束下的线圈优化设计效果。针对该研... 无线电能传输(WPT)系统谐振网络的参数设计对于电能安全高效传输至关重要。在满足系统多约束条件下实施谐振线圈的优化设计是一种十分实用且高效快速的方法。然而,传统的单层线圈绕制方案无法满足多约束下的线圈优化设计效果。针对该研究问题,本文提出了一种内外双层线圈的设计方法,其不仅能够快速设计出满足WPT系统多边界约束条件的线圈,而且通过合理优化线圈内外层匝数分布使得线圈在宽耦合系数范围内具有优异的传输性能,并通过搭建1.15 kW实验平台,验证所提方法的有效性。 展开更多
关键词 无线电能传输 内外双层线圈 多边界约束
在线阅读 下载PDF
泉州湾高铁斜拉桥桥塔温差特性及极值研究
17
作者 戴公连 罗泽江 +1 位作者 张昂 王芬 《华中科技大学学报(自然科学版)》 北大核心 2025年第2期40-46,共7页
为研究沿海地区桥塔温差的时变特征和统计特征,对泉州湾高铁斜拉桥桥塔进行了1 a的现场温度监测试验.根据温度实测数据和气象数据,分析了桥塔壁内外温差与线性温差的时变特征.采用梯度提升回归树算法建立了桥塔各测点的温度预测模型,由... 为研究沿海地区桥塔温差的时变特征和统计特征,对泉州湾高铁斜拉桥桥塔进行了1 a的现场温度监测试验.根据温度实测数据和气象数据,分析了桥塔壁内外温差与线性温差的时变特征.采用梯度提升回归树算法建立了桥塔各测点的温度预测模型,由此得到桥塔测点的历史温度预测值.基于等效变形原则,经计算和整理得桥塔截面线性温差预测值的年极值样本,结合最大熵模型和Bootstrap法确定了100 a重现期下的桥塔线性温差代表值.结果表明:桥塔的壁内外温差始终呈指数分布,向阳面温差冬季更高,背阳面温差夏季更高.桥塔顺桥向和横桥向的线性温差均为冬季最高.100 a重现期下的顺桥向与横桥向的线性温差代表值分别为6.24℃,6.77℃. 展开更多
关键词 混凝土桥塔 现场试验 内外壁温差 线性温差 梯度提升回归树算法 极值分析
原文传递
模范教师的精神品质与形成逻辑——全国教书育人楷模杨毛吉老师专访
18
作者 李晓华 周晏竹 《当代教育与文化》 2025年第3期94-101,共8页
“乐教爱生、甘于奉献的仁爱之心”是教育家精神品质之一。杨毛吉老师扎根青海基础教育29年,对教育事业的忠诚和对学生的热爱构成其以“仁爱之心”为突出表现的教育家精神。其丰富的从教经历彰显出“视生为子”是“仁爱之心”的基础;“... “乐教爱生、甘于奉献的仁爱之心”是教育家精神品质之一。杨毛吉老师扎根青海基础教育29年,对教育事业的忠诚和对学生的热爱构成其以“仁爱之心”为突出表现的教育家精神。其丰富的从教经历彰显出“视生为子”是“仁爱之心”的基础;“为了孩子一生幸福”的教育理想与“热爱教育事业”的教育情怀、“行为世范”的人格修养是“仁爱之心”的内在驱力;教育实践积累、持续性自我反思与改进是“仁爱之心”的外在实践行动。杨毛吉老师期望教师应以积极心态迎接挑战,以“视生为子”为初心,在内外共同驱动中成长为具有“乐教爱生、甘于奉献的仁爱之心”的模范教师。 展开更多
关键词 教育家精神 仁爱之心 精神品质 内在驱力 实践行动
在线阅读 下载PDF
含电流内环的构网型MMC新型交流电压构建策略及参数设计 被引量:1
19
作者 刘黎 杨仁炘 +3 位作者 施刚 张琛 张建文 蔡旭 《电力系统保护与控制》 北大核心 2025年第7期27-39,共13页
构网型控制是电力电子变流器支撑新能源主导电力系统稳定运行的一种有效技术途径。高压大功率场景下,构网变流器通常采用模块化多电平(modular multilevel converter,MMC)拓扑。MMC无集中滤波电容、难以获取并网电流前馈的特性使得常规... 构网型控制是电力电子变流器支撑新能源主导电力系统稳定运行的一种有效技术途径。高压大功率场景下,构网变流器通常采用模块化多电平(modular multilevel converter,MMC)拓扑。MMC无集中滤波电容、难以获取并网电流前馈的特性使得常规构网型控制中,交流电压-交流电流级联控制回路的性能恶化。为此,提出了一种新型交流电压控制策略,在保留电流内环限流能力的同时,将电流内环通过戴维南-诺顿等效变换成受控电压源串联虚拟阻抗的形式,实现了与同步发电机类似的端电压构建机制。在此基础上,基于小信号状态空间模型对控制环节及控制参数进行了优化设计。最后,在PSCAD/EMTDC平台进行仿真,结果验证了所提新型构网策略及参数设计方法的有效性。 展开更多
关键词 模块化多电平换流器 柔性直流输电 构网型控制 电流内环 交流电压控制
在线阅读 下载PDF
弄岗喀斯特季节性雨林常见树种树皮厚度的变异及其环境解释
20
作者 王艳萍 王斌 +6 位作者 陆芳 陶旺兰 李健星 黄甫昭 郭屹立 向悟生 李先琨 《生态学杂志》 北大核心 2025年第5期1436-1447,共12页
树皮由维管形成层以外的所有组织组成,其功能特性反映植物重要的生态适应策略。为揭示弄岗喀斯特季节性雨林常见树种树皮厚度在不同类群和功能群间的差异以及生物因子和环境因子对树皮厚度的影响,以弄岗15 hm^(2)永久森林监测样地内多... 树皮由维管形成层以外的所有组织组成,其功能特性反映植物重要的生态适应策略。为揭示弄岗喀斯特季节性雨林常见树种树皮厚度在不同类群和功能群间的差异以及生物因子和环境因子对树皮厚度的影响,以弄岗15 hm^(2)永久森林监测样地内多度大于20的128种常见树种为研究对象,分析不同类群和功能群之间树皮厚度的差异,以及生物因子和环境因子对树皮厚度的影响。结果发现:弄岗128种常见树种的树皮总厚度、外树皮厚度、内树皮厚度均值分别为2.95、0.70、2.26 mm;亚麻科(Linaceae)、紫葳科(Bignoniaceae)、茶茱萸科(Icacinaceae)的树皮相对较厚;树皮厚度在不同类群和功能群间均呈显著差异,且内树皮厚度>外树皮厚度;不同功能群中,落叶种>常绿种(外树皮厚度除外),乔木种>小乔木种>灌木种;树皮厚度的系统发育信号较弱,因此树皮厚度主要受生境因素影响;在影响树皮厚度的多种生物因子中,物种因子的解释率最高;此外,树皮厚度变异受地形因子和土壤因子驱动,不同群丛位置存在相似性,树皮总厚度与林分因子和环境因子均存在相关性。综上,弄岗喀斯特季节性雨林群落内树种的树皮厚度较薄,不同树种间和功能群间的树皮厚度存在较大差异,表明这些树种对当地湿润气候的适应性,环境因子对树皮厚度的解释揭示了树种通过调整树皮厚度来适应不同环境条件和生态位的策略。 展开更多
关键词 树皮总厚度 内树皮厚度 外树皮厚度 季节性雨林 生态位分化 环境因子
原文传递
上一页 1 2 82 下一页 到第
使用帮助 返回顶部