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Dynamical Mechanisms of Effects of Landslides on Long Distance Oil and Gas Pipelines 被引量:7
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作者 MA Qingwen WANG Chenghua KONG Jiming 《Wuhan University Journal of Natural Sciences》 EI CAS 2006年第4期820-824,共5页
According to the investigations on the oil and gas pipelines such as the Lan-Cheng-Chong pipeline and the Southwest pipeline, there are two ways of laying pipeline: pipelines paralleling (approximately) to the main... According to the investigations on the oil and gas pipelines such as the Lan-Cheng-Chong pipeline and the Southwest pipeline, there are two ways of laying pipeline: pipelines paralleling (approximately) to the main slide direction and pipelines perpendicular (approximately) to the main slide direction. If earth-retaining walls have been built for pipelines paralleling to the main slide direction, they will prevent the lands from sliding; On the contrary, without earth-retaining walls, the sharp broken rocks in the backfilling soil will scratch the safeguard of the pipeline when the landslides take place. Pipelines perpendicular to the main slide direction can be classified into four types according to the relative positions between pipelines and landslides: Pipelines over the slide planes, pipelines inside the fracture strips of slide planes, pipelines below the slide planes and pipelines behind the backsides of landslides. The different dynamical mechanisms of the process in which landslide acts against pipelines are analyzed based on whether the pipelines are equipped with fixed frusta, because the sliding resistance depends on whether and how many fixed frusta are equipped and the distance between frusta. 展开更多
关键词 LANDSLIDE long distance oil and gas pipeline dynamical mechanism
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Scheme of long distance power supply for electrified railway traction network based on traction cable 被引量:1
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作者 Hui Wang Qunzhan Li +2 位作者 Wei Liu Chuang Wang Tongtong Liu 《Railway Sciences》 2022年第1期114-130,共17页
Purpose–The traction cable is paralleled with the existing traction network of electrified railway through transverse connecting line to form the scheme of long distance power supply for the traction network.This pap... Purpose–The traction cable is paralleled with the existing traction network of electrified railway through transverse connecting line to form the scheme of long distance power supply for the traction network.This paper aims to study the scheme composition and power supply distance(PSD)of the scheme.Design/methodology/approach–Based on the structure of parallel traction network(referred to as“cable traction network(CTN)”),the power supply modes(PSMs)are divided into cableþdirect PSM and cableþautotransformer(AT)PSM(including Japanese mode,French mode and new mode).Taking cableþJapanese AT PSM as an example,the scheme of long distance power supply for CTN under the PSMs of co-phase and out-of-phase power supply are designed.On the basis of establishing the equivalent circuit model and the chain circuit model of CTN,taking the train working voltage as the constraint condition,and based on the power flow calculation of multiple train loads,the calculation formula and process for determining the PSD of CTN are given.The impedance and PSD of CTN under the cableþAT PSM are simulated and analyzed,and a certain line is taken as an example to compare the scheme design.Findings–Results show that the equivalent impedance of CTN under the cableþAT PSM is smaller,and the PSD is about 2.5 times of that under the AT PSM,which can effectively increase the PSD and the flexibility of external power supply location.Originality/value–The research content can effectively improve the PSD of traction power supply system and has important reference value for the engineering application of the scheme. 展开更多
关键词 Traction cable Electrified railway Traction network long distance power supply Voltage drop Power flow calculation
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The Role that φ-Features Play in Long Distance Binding
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作者 PAN Shi wen (Foreign Languages College,Guangxi Normal University, Guilin 541004, China) 《广西师范大学学报(哲学社会科学版)》 2002年第S2期1-12,共12页
Chinese long distance binding is explored in terms of a feature orientated approach: a long distance anaphor with barren or impoverished φ features is obliged to acquires φ features (or phi features) from its adjace... Chinese long distance binding is explored in terms of a feature orientated approach: a long distance anaphor with barren or impoverished φ features is obliged to acquires φ features (or phi features) from its adjacent NPs in its upward movement at LF, and that this feature obtaining process, governed by rules that are summarized in terms of Feature Saturation Process (FSP), provides answers to long distance binding. Accordingly, binding is seen as an instance of a perfect match of features possessed by a saturated anaphor and an NP at LF. An anaphor is bound when it moves to INFL with its φ features matched with a feature functioning NP, whereas a middle way anaphor with unsaturated φ features is not bound. This approach satisfactorily explains the binding relations in sentences of long distance coreference and providing alternative answers to other issues of binding. It is further shown that the binding of Chinese reflexive ziji (自己)to its antecedent(s) results from a sequence of local dependency through movement. 展开更多
关键词 ANAPHOR Chinese long distance binding ziji FEATURE SATURATION Principle A FSP
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HF FIELD STRENGTH MEASUREMENTS OVER THE VERY LONG DISTANCE
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作者 Du Junhu Sun Xianru China Research Institute of Radiowave Propagation, Xinxiang 453003 《Chinese Journal of Polar Science》 1991年第1期60-67,共8页
It was ascertained that there is a great margin between the theoretical values and experimental medians of the field strength of RWM and RID signals during high solar activity period at Chinese Great Wall Station on A... It was ascertained that there is a great margin between the theoretical values and experimental medians of the field strength of RWM and RID signals during high solar activity period at Chinese Great Wall Station on Antarctica. The calculated values are, on average, less than the experimental, especially on the propagation path between RID and Antarctica. The field strength by the experiment may be used as the basic data for the research of HF propagation over the very long distance. Because of the large deviation it seems to be necessary to study HF propagation over the very long distance in details, especially the propagation model. 展开更多
关键词 field strength long distance RWM RID ANTARCTICA
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Experimental Investigation on Thermal Characteristics of Long Distance Loop Heat Pipes
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作者 ZHAO Ya’nan YAN Tao LIANG Jingtao 《Journal of Thermal Science》 SCIE EI CAS CSCD 2022年第3期741-750,共10页
Loop heat pipes(LHPs)are attractive two-phase thermal control devices for satellites,electronics and many other applications.They are capable of transporting heat efficiently for long distances up to several meters at... Loop heat pipes(LHPs)are attractive two-phase thermal control devices for satellites,electronics and many other applications.They are capable of transporting heat efficiently for long distances up to several meters at any orientation.This paper investigated the heat transfer characteristics of loop heat pipes with long distances and small diameter transport lines.Small stainless steel tubes of 2 mm and 3 mm in inner diameters were chosen as liquid lines and vapor lines of the LHPs.The local thermal resistances in the evaporator of the 6 m-LHP were researched and analyzed,which indicated that the thermal resistance between the aluminum block and the vapor in the vapor channel accounted for a major proportion of the total thermal resistance.The effect of heat sink temperatures on the performance of the 6 m-LHP were compared with 10°C,15°C,20°C and 25°C cooling water temperatures.Moreover,the thermal characteristics of LHPs with transport distances of 2 m and 16 m were also experimentally investigated.The 16 m-LHP could achieve a heat transfer capacity of 100 W and the 2 m-LHP could reach more than 339 W,on the premise of the evaporator temperature below 100°C.The thermal resistance of the 2 m-LHP could achieve 0.125°C/W. 展开更多
关键词 loop heat pipe thermal management heat transport long distance thermal resistance
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Broadband IP Stream Transmission Experiments over Global and Long Distance Networks
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作者 Kimio Oguchi Tetsuro Fujii +3 位作者 Atsushi Takahara Toshiaki Miyazaki Kazuo Hagimoto Sadayasu Ono 《光学学报》 EI CAS CSCD 北大核心 2003年第S1期527-528,共2页
Super High Definition (SHD) movies were successfully transmitted as streaming contents at about 300 Mbps for the first time over a long distance IP network (more than 3,000 km), in conjunction with the experimental ve... Super High Definition (SHD) movies were successfully transmitted as streaming contents at about 300 Mbps for the first time over a long distance IP network (more than 3,000 km), in conjunction with the experimental verification of traffic control and scalable multicast technologies. 展开更多
关键词 IP on OVER Broadband IP Stream Transmission Experiments over Global and long distance Networks
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Novel Double-Damped Tuned AC Filters in HVDC Systems
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作者 Rana Shaheer Mehmood Asif Hussain +1 位作者 Usman Ali Muhammad Tariq Mahmood 《Computers, Materials & Continua》 SCIE EI 2023年第4期1467-1482,共16页
This paper presents a performance analysis of novel doubledampedtuned alternating current (AC) filters in high voltage direct current(HVDC) systems. The proposed double-damped tuned AC filters offer theadvantages of i... This paper presents a performance analysis of novel doubledampedtuned alternating current (AC) filters in high voltage direct current(HVDC) systems. The proposed double-damped tuned AC filters offer theadvantages of improved performance of HVDC systems in terms of betterpower quality, high power factor, and lower total harmonic distortion (THD).The system under analysis consists of an 878 km long HVDC transmissionline connecting converter stations at Matiari and Lahore, two major cities inPakistan. The main focus of this research is to design a novel AC filter usingthe equivalent impedance method of two single-tuned and double-dampedtuned AC filters. Additionally, the impact of the damping resistor on the ACchannel is examined. TheTHDof theHVDCsystem with and without currentAC filters was also compared in this research and a double-damped tuned ACfilter was proposed. The results of the simulation represent that the proposeddouble-damped tuned AC filter is far smaller in size, offers better powerquality, and has a much lower THD compared to the AC filters currently inplace in the converter station. The simulation analysis was carried out utilizingpower systems computer-aided design (PSCAD) software. 展开更多
关键词 Double-damped tuned AC filters HARMONICS high voltage DC systems long distance transmission power quality total harmonic distortion
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Smart Elevator Systems
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作者 Kheir Al-Kodmany 《Journal of Mechanical Materials and Mechanics Research》 2023年第1期41-53,共13页
Effective vertical mobility is a crucial element in the design and construction of tall buildings.This paper reviews recent“smart”developments in elevator technologies and analyzes how they affect the construction a... Effective vertical mobility is a crucial element in the design and construction of tall buildings.This paper reviews recent“smart”developments in elevator technologies and analyzes how they affect the construction and operation of tall buildings.In an approachable and non-technical discourse,it maps out,arranges,and compiles complicated and dispersed information on various elements of elevator design.It discusses hardware-based innovations,such as AC and gearless motors,machine-room-less(MRL)elevators,regenerative drives,elevator ropes,and LED lighting,as well as software-based solutions,such as destination dispatching systems,people flow solutions,standby mode,and predictive maintenance applications.Future vertical transportation models are also discussed,including multi-directional elevators and circulating multi-car elevators.Lastly,the paper suggests fruitful avenues for further studies on the subject,such as robotics,3D printing,and the impact of the COVID-19 pandemic on elevator design. 展开更多
关键词 Energy efficiency Energy conservation long distances HARDWARE SOFTWARE APPLICATIONS
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Paleozoic Tectono-Metallogeny in the Tianshan-Altay Region,Central Asia 被引量:6
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作者 WAN Tianfeng ZHAO Qingle WANG Qianqian 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2015年第4期1120-1132,共13页
The research on Paleozoic tectonics and endogenic metallogeny in the Tianshan-Altay region of Central Asia is an important and significant project. The Altay region, as a collision zone of the Early Paleozoic (500-39... The research on Paleozoic tectonics and endogenic metallogeny in the Tianshan-Altay region of Central Asia is an important and significant project. The Altay region, as a collision zone of the Early Paleozoic (500-397 Ma), and the Tianshan region, as a collision zone of the early period in the Late Paleozoic (Late Devonian-Early Carboniferous, 385-323 Ma), are all the result of nearly N-S trending shortening and collision (according to recent magnetic orientation). In the Late Devonian-Early Carboniferous period (385-323 Ma), regional NW trending faults displayed features of dextral strike-slip motion in the Altay and Junggar regions. In the Tianshan region, nearly EW-trending regional faults are motions of the thrusts. However, in the Late Carboniferous-Early Permian period (323-260 Ma), influenced by the long-distance effect induced from the Ural collision zone, those areas suffered weaker eastward compression, the existing NW trending faults converted into sinistral strike-slip in the Altay and Junggar regions, and the existing nearly E-W trending faults transferred into dextral strike-slip faults in the Tianshan region. The Rocks of those regions in the Late Carboniferous-Early Permian period (323-260 Ma) were moderately ruptured to a certain tension-shear, and thus formed a number of world famous giant endogenic metal ore deposits in the Tianshan-Altay region. As to the Central Asian continent, the most powerful collision period may not coincide with the most favorable endogenic metallogenic period. It should be treated to "the orogenic metallogeny hypothesis" with caution in that region. 展开更多
关键词 tectonics endogenic metallogeny long distance effect Tianshan-Altay region
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Restructuring and the Proper Syntactic Analysis
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作者 Hong-Pin Im 《宏观语言学》 2021年第1期1-32,共32页
This paper aims to make it clear that syntactic analysis should be based on the lexical information given in the lexicon.For this purpose,lexical information of the syntactic argument is to be taken the form like[VP N... This paper aims to make it clear that syntactic analysis should be based on the lexical information given in the lexicon.For this purpose,lexical information of the syntactic argument is to be taken the form like[VP NKP,_,DKP,AKP]for the ditransitive verb give in English.The argument structure projects to syntactic structure.The NKP in this structure becomes VP-subject,but there is another subject called S-subject(Sentence-Subject)below S node.This amounts to Two-Subject Hypothesis for English.Between these two subjects,there intervene Conjugation-Like Elements,enriched by close examination of English verbal conjugation.Two-Subject Hypothesis perfectly accounts for peculiarities of the Expletive There(ET)construction.Restructuring can also explain the so-called Long Distance Wh-interrogative without introducing Wh-movement,and it can also explain why the imperative verbs are taking the base forms.It can also explain the characteristics of adjective imperatives by the same principles as applied to verbal imperatives.We try to deal with the other subtle problems,to get fruitful results.Restructuring approach,we think,provides more convincing explanations than the movement one. 展开更多
关键词 RESTRUCTURING sentence type Two-Subject Hypothesis Conjugation-Like Element ET construction long distance Wh-interrogatives adjective imperatives
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Web Service在远程教育平台虚拟学习社区中的应用 被引量:3
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作者 徐恩友 《武汉工程职业技术学院学报》 2004年第2期50-54,共5页
本文主要参照现代远程教育标准规范并结合WebService技术 ,给出了一个远程教育的虚拟学习社区模型。该社区采用了基于WebService的三层架构模式 ,有利于系统的模块化设计和开发。
关键词 远程教育 WEB SERVICE 虚拟学习社区
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Compact long-working-distance laser-diode-based photoacoustic microscopy with a reflective objective
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作者 邓丽军 陈奇 +3 位作者 白杨 刘国栋 曾吕明 纪轩荣 《Chinese Optics Letters》 SCIE EI CAS CSCD 2021年第7期56-61,共6页
Photoacoustic microscopy(PAM) has quickly developed into a noninvasive biomedical imaging technique to achieve detection, diagnosis, and monitoring.Compared with Q-switched neodymium-doped yttrium aluminum garnet or o... Photoacoustic microscopy(PAM) has quickly developed into a noninvasive biomedical imaging technique to achieve detection, diagnosis, and monitoring.Compared with Q-switched neodymium-doped yttrium aluminum garnet or optical parametric oscillator lasers, a low-cost and small-size laser diode(LD) used as an alternative light source is conducive to achieving the miniaturization and integration for preclinical transformation.However, the LD’s low peak output power needs the high numerical aperture objective to attain tight focus, which limits the working distance(WD) of the system in only2–3 mm, resulting in not achieving the backward coaxial confocal mode.Here, we present a compact visible LD-based PAM system with a reflective objective to achieve a 22 mm long WD and a 10 μm lateral resolution.Different depth subcutaneous microvascular networks in label-free mouse ears have successfully reappeared in vivo with a signal-to-noise ratio up to14 d B by a confocal alignment.It will be a promising tool to develop into a handy tool for subcutaneous blood vessel imaging. 展开更多
关键词 photoacoustic microscopy long working distance laser diode reflective objective
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Compact in situ microscope for photoelectron spectroscopy via two-mirror reflection
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作者 岳晨阳 江虹 +4 位作者 李天植 姚思研 曾生跃 许晓军 张超凡 《Chinese Optics Letters》 SCIE EI CAS CSCD 2023年第6期43-47,共5页
Photoelectron spectroscopy is a powerful tool in characterizing the electronic structure of materials.To investigate the specific region of interest with high probing efficiency,in this work we propose a compact in si... Photoelectron spectroscopy is a powerful tool in characterizing the electronic structure of materials.To investigate the specific region of interest with high probing efficiency,in this work we propose a compact in situ microscope to assist photoelectron spectroscopy.The configuration of long objective distance of 200 mm with two-mirror reflection has been introduced.Large magnification of 5×to 100×,lateral resolution of 4.08μm,and longitudinal resolution of 4.49μm have been achieved.Meanwhile,the testing result shows larger focal depth of this in situ optical microscope.Similar configurations could also be applied to other electronic microscopes to improve their probing capability. 展开更多
关键词 photoelectron spectroscopy in situ optical microscope long objective distance large magnification
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Volume Transmission and Its Different Forms in the Central Nervous System 被引量:6
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作者 Kjell Fuxe Dasiel O.Borroto-Escuela +2 位作者 Wilber Romero-Fernandez 张维波 Luigi F.Agnati 《Chinese Journal of Integrative Medicine》 SCIE CAS 2013年第5期323-329,共7页
Volume transmission (VT) is a widespread mode of intercellular communication that occurs in the extracellular fluid (ECF) and in the cerebrospinal fluid (CSF) of the brain with VI signals moving from source to t... Volume transmission (VT) is a widespread mode of intercellular communication that occurs in the extracellular fluid (ECF) and in the cerebrospinal fluid (CSF) of the brain with VI signals moving from source to target cells via energy gradients leading to diffusion and convection (flow). The VT channels are diffuse forming a plexus in the extracellular space, while in wiring transmission (WT) the channels (axons, terminals) are private. The speed is slow (seconds-minutes) in VT while rapid in the millisecond range in w-r. The extracellular space is the substrate for VT, which is modulated by the extracellular matrix. Extrasynaptic VT is linked to synaptic transmission and likely often takes place due to incomplete diffusion barriers with the synaptic transmitter reaching extrasynaptic domains of the pre-and post-synaptic membrane of the synapse, the astroglia, and even adjacent synapses. Indications exist for the existence of striatal D2-1ike receptor-mediated extrasynaptic form of dopamine (DA) VT at the local circuit level in vivo in the human striatum. Synaptic glutamate via extrasynaptic VT can act on extrasynaptic metabotropic glutamate receptors located on the astroglia leading to Ca2~ mediated astrocytic glutamate release into the extracellular space (ECS). Long distance peptide VT and CSF VT is the major long distance VT with distances more than 1 mm and flow in the CSF. Indications for long distance vr of beta-endorphin and oxytocin are obtained. We propose that monogamy in the female prairie vole may take place through an increase in oxytocin v-r, especially in nucleus accumbens. Release of extracellular vesicles containing receptors, proteins, RNAs and mtDNA from cellular networks in the central nervous system (CNS) into the ECF and CSF may be a fundamental communication in the CNS. It represents a special form of volume transmission, the Roamer subtype of VT. It may greatly contribute to dynamic events of synaptic plasticity but also to spread of pathological proteins in protein conformational disorders. V'i" also occurs in the peripheral nervous system and associated cells. Short and long distance VT may take place in meridian channels via diffusion and flow in the interstitial fluid. Acupuncture can produce VT signals by releasing transmitters and modulators from nerve terminals and mast cells. 展开更多
关键词 extrasynaptic volume transmission long distance volume transmission Roamer type of volume transmission Chinese medicine MERIDIAN
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Distinct potential aerosol masses under different scenarios of transport at a suburban site of Beijing 被引量:6
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作者 Biwu Chu Yongchun Liu +5 位作者 Qingxin Ma Jinzhu Ma Hong He Gang Wang Shuiyuan Cheng Xinming Wang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2016年第1期52-61,共10页
In order to evaluate the secondary aerosol formation potential at a suburban site of Beijing,in situ perturbation experiments in a potential aerosol mass(PAM) reactor were carried out in the winter of 2014.The varia... In order to evaluate the secondary aerosol formation potential at a suburban site of Beijing,in situ perturbation experiments in a potential aerosol mass(PAM) reactor were carried out in the winter of 2014.The variations of secondary aerosol formation as a function of time,OH exposure,and the concentrations of gas phase pollutants and particles were reported in this study.Two periods with distinct secondary aerosol formation potentials,marked as Period Ⅰ and Period Ⅱ,were identified during the observation.In Period Ⅰ,the secondary aerosol formation potential was high,and correlated well to the air pollutants,i.e.,SO2,NO2,and CO.The maximal secondary aerosol formation was observed with an aging time equivalent to about 3 days of atmospheric oxidation.In period Ⅱ,the secondary aerosol formation potential was low,with no obvious correlation with the air pollutants.Meanwhile,the aerosol mass decreased,instead of showing a peak,with increasing aging time.Backward trajectory analysis during the two periods confirmed that the air mass in Period Ⅰwas mainly from local sources,while it was attributed mostly to long distance transport in Period Ⅱ.The air lost its reactivity during the long transport and the particles became highly aged,resulting in a low secondary aerosol formation potential.Our experimental results indicated that the in situ measurement of the secondary aerosol formation potential could provide important information for evaluating the contributions of local emission and long distance transport to the aerosol pollution. 展开更多
关键词 Potential aerosol mass Local emission long distance transport Aging In situ perturbation experiments
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Root osmotic sensing from local perception to systemic responses 被引量:2
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作者 Lucille Gorgues Xuelian Li +2 位作者 Christophe Maurel Alexandre Martiniere Philippe Nacry 《Stress Biology》 2022年第1期249-269,共21页
Plants face a constantly changing environment,requiring fine tuning of their growth and development.Plants have therefore developed numerous mechanisms to cope with environmental stress conditions.One striking exam-pl... Plants face a constantly changing environment,requiring fine tuning of their growth and development.Plants have therefore developed numerous mechanisms to cope with environmental stress conditions.One striking exam-ple is root response to water deficit.Upon drought(which causes osmotic stress to cells),plants can among other responses alter locally their root system architecture(hydropatterning)or orientate their root growth to optimize water uptake(hydrotropism).They can also modify their hydraulic properties,metabolism and development coordi-nately at the whole root and plant levels.Upstream of these developmental and physiological changes,plant roots must perceive and transduce signals for water availability.Here,we review current knowledge on plant osmotic per-ception and discuss how long distance signaling can play a role in signal integration,leading to the great phenotypic plasticity of roots and plant development. 展开更多
关键词 DROUGHT Water deficit perception Local signaling long distance signaling Local water deficit Adaptive development
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A comparison of the pre-calling period between Japanese and southeastern Asian populations of Spodoptera litura 被引量:1
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作者 MIKA MURATA HIROYUKI MATSUKI +1 位作者 RYOHEI YAMAOKA SUMIO TOJO 《Insect Science》 SCIE CAS CSCD 2006年第3期211-216,共6页
The pre-calling behavior of female adults of the common cutworm, Spodoptera litura (Lepidoptera: Noctuidae) collected in southern Japan and southeastern Asian countries was investigated. Most females started callin... The pre-calling behavior of female adults of the common cutworm, Spodoptera litura (Lepidoptera: Noctuidae) collected in southern Japan and southeastern Asian countries was investigated. Most females started calling on days 1-4 after adult emergence. In three populations obtained in Saga prefecture in Kyushu mainland, Japan, two different patterns of pre-calling period (PCP) were observed: one was the above-mentioned pattern shown by most individuals, and the other was a pattern in which females sexually matured within several hours after emergence. Diel periodicity was shown in the time of calling activity, and its pattern varied among the populations. Pre-calling period was stable over successive generations in the laboratory. 展开更多
关键词 geographical variation long distance migration pre-calling period Spodoptera litura
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Recent introduction of an allodapine bee into Fiji: A new model system for understanding biological invasions by pollinators
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作者 Scott V. C. Groom Marika V. Tuiwawa +1 位作者 Mark I. Stevens Michael P. Schwarz 《Insect Science》 SCIE CAS CSCD 2015年第4期532-540,共9页
Morphology-based studies have suggested a very depauperate bee fauna for islands in the South West Pacific, and recent genetic studies since have indicated an even smaller endemic fauna with many bee species in this r... Morphology-based studies have suggested a very depauperate bee fauna for islands in the South West Pacific, and recent genetic studies since have indicated an even smaller endemic fauna with many bee species in this region resulting from human-aided dispersal. These introduced species have the potential to both disrupt native pollinator suites as well as augment crop pollination, but for most species the timings of introduction are unknown. We examined the distribution and nesting biology of the long-tongued bee Braunsapis puangensis that was first recorded from Fiji in 2007. This bee has now become widespread in Fiji and both its local abundance and geographical range are likely to increase dramatically. The impacts of this invasion are potentially enormous for agriculture and native ecosystems, but they also provide opportunities for understanding how social insect species adapt to new environments. We outline the major issues associated with this recent invasion and argue that a long-term monitoring study is needed. 展开更多
关键词 Allodapini exotic species Fiji long distance dispersal pollinatorcompetition
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2D Correlative-Chain Conditional Random Fields for Semantic Annotation of Web Objects
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作者 丁艳辉 李庆忠 +1 位作者 董永权 彭朝晖 《Journal of Computer Science & Technology》 SCIE EI CSCD 2010年第4期761-770,共10页
Semantic annotation of Web objects is a key problem for Web information extraction. The Web contains an abundance of useful semi-structured information about real world objects, and the empirical study shows that stro... Semantic annotation of Web objects is a key problem for Web information extraction. The Web contains an abundance of useful semi-structured information about real world objects, and the empirical study shows that strong two-dimensional sequence characteristics and correlative characteristics exist for Web information about objects of the same type across different Web sites. Conditional Random Fields (CRFs) are the state-of-the-art approaches taking the sequence characteristics to do better labeling. However, as the appearance of correlative characteristics between Web object elements, previous CRFs have their limitations for semantic annotation of Web objects and cannot deal with the long distance dependencies between Web object elements efficiently. To better incorporate the long distance dependencies, on one hand, this paper describes long distance dependencies by correlative edges, which are built by making good use of structured information and the characteristics of records from external databases; and on the other hand, this paper presents a two-dimensional Correlative-Chain Conditional Random Fields (2DCC-CRFs) to do semantic annotation of Web objects. This approach extends a classic model, two-dimensional Conditional Random Fields (2DCRFs), by adding correlative edges. Experimental results using a large number of real-world data collected from diverse domains show that the proposed approach can significantly improve the semantic annotation accuracy of Web objects. 展开更多
关键词 Web information extraction semantic annotation conditional random fields long distance dependencies
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