检索结果-南通市图书馆

On localization with robust power control for safety critical wireless sensor networks

控制理论与应用（英文版） 2011年第1期9卷 83-92页

作者： Michael j. WALSH Anthony FEE j.hn BARTON Brendan O'FLYNN Martin j. HAYES Cian O'MATHUNA Clarity Center for Web Technologies Microsystems Centre-Tyndall National Institute Lee MaltingsUniversity College CorkCorkIreland Wireless Access Research Center University of LimerickLimerickIreland

A hybrid methodology is proposed for use in low power, safety critical wireless sensor network applications, where quality-of-service orientated transceiver output power control is required to operate in parallel with radio frequency-based localization. The practical implementation is framed in an experimental procedure designed to track a moving agent in a realistic indoor environment. An adaptive time synchronized approach is employed to ensure the positioning technique can operate effectively in the presence of dataloss and where the transmitter output power of the mobile agent is varying due to power control. A deterministic multilateration-based positioning approach is adopted and accuracy is improved by filtering signal strength measurements overtime to account for multipath fading. The location estimate is arrived at by employing least-squares estimation. Power control is implemented at two separate levels in the network topology. First, power control is applied to the uplink between the tracking reference nodes and the centralized access point. A number of algorithms are implemented highlighting the advantage associated with using additional feedback bandwidth, where available, and also the need for effective time delay compensation. The second layer of power control is implemented on the uplink between the mobile agent and the access point and here quantifiable improvements in quality of service and energy efficiency are observed. The hybrid paradigm is extensively tested experimentally on a fully compliant 802.15.4 testbed, where mobility is considered in the problem formulation using a team of fully autonomous robots.

关键词： Wireless sensor network Power control Localization

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Sexual selection affects the sizes of the mammalian prostate gland and seminal vesicles

引用

Current Zoology 2009年第1期55卷 1-8页

作者： Matthew j. ANDERSON Alan F. DIXSON Conservation and Research for Endangered Species Zoological Society of San Diego School of Biological Sciences Victoria University of Wellington

The accessory reproductive glands of male mammals contribute the bulk of the secretions in which spermatozoa are transported to the female tract during copulation. Despite their morphological diversity, and the chemical complexity of their products, little is known about the possible effects of sexual selection upon these glands in mammals. here we consider the seminal vesicles and prostate glands in a sample of 89 species and 60 genera representing 8 Orders of mammals. The sizes of the accessory glands are analysed in relation to body weight and testes weight. Both the seminal vesicles size and prostate size （corrected for body weight） correlate positively with relative testes size in this sample; this finding remains highly significant after application of procedures to correct for possible phylogenetic biases in the data set. The accessory reproductive glands are also significantly larger in those mammals which have large relative testes sizes, and in which the likelihood of sperm competition is greatest. These results support the hypothesis that sexual selection has played an important role in the evolution of the mammalian prostate gland and seminal vesicles.

关键词： Mammals Prostrate gland Seminal vesicles Sexual selection Sperm competition

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

MODELING HEADCUT DEVELOPMENT AND MIGRATION IN UPLAND CONCENTRATED FLOWS

引用

International j.urnal of Sediment Research 2005年第4期20卷 281-294页

作者： Sean j. BENNETT Carlos V. ALONSO Department of Geography University at Buffalo Buffalo NY 14261-0055 USA USDA-ARS National Sedimentation Laboratory P.O. Box 1157 Oxford MS 38655

On hillslopes and agricultural fields, discrete areas of intense, localized soil erosion commonly take place in the form of migrating headcuts. These erosional features significantly increase soil loss and landscape degradation, yet the unsteady, transient, and migratory habits of headcuts complicate their phenomenological and erosional characterization. here a unique experimental facility was constructed to examine actively migrating headcuts typical of upland concentrated flows. Essential components of the facility include a deep soil cavity with external drainage, rainfall simulator, capacity for overland flow, and a video recording technique for data collection. Results from these experiments show that: (1) after a short period of adj.stment, headcut migration attained a steady-state condition, where the rate of migration, scour hole geometry, and sediment discharge remain constant with time; (2) boundary conditions of higher rates of overland flow, steeper bed slopes, and larger initial headcut heights produced systematically larger scour holes with higher rates of soil erosion; and (3) during migration, the turbulent flow structure within the scour hole remained unchanged, consisting of an overfall nappe at the brink transitioning into a reattached wall j.t with two recirculation eddies within the plunge pool. The systematic behavior of headcut development and migration enabled the application of modified j.t impingement theory to predict with good success the characteristics of the impinging j.t, the depth of maximum scour, the rate of headcut migration, and the rate of sediment erosion. These laboratory data and the analytical formulation can be used in conj.nction with soil erosion prediction technology to improve the management of agricultural areas impacted by headcut development and ephemeral gully erosion.

关键词： Soil erosion Headcuts Rills Gullies j.t impingement

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Lithographically directed assembly of one-dimensional DNA nanostructures via bivalent binding interactions

引用

Nano Research 2013年第6期6卷 409-417页

作者： Risheng Wang Matteo Palma Erika Penzo Shalom j. Wind Department of Applied Physics and Applied Mathematics Columbia University 500 West 120th Street New York NY 10027 USA Department of Chemistry Columbia University 500 West 120th Street New York NY 10027 USA

In order to exploit the outstanding physical properties of one-dimensional （1D） nanostructures such as carbon nanotubes and semiconducting nanowires and nanorods in future technological applications, it will be necessary to organize them on surfaces with precise control over both position and orientation. here, we use a 1D rigid DNA motif as a model for studying directed assembly at the molecular scale to lithographically patterned nanodot anchors. By matching the inter-nanodot spacing to the length of the DNA nanostructure, we are able to achieve nearly 100% placement yield. By varying the length of single-stranded DNA linkers bound covalently to the nanodots, we are able to study the binding selectivity as a function of the strength of the binding interactions. We analyze the binding in terms of a thermodynamic model which provides insight into the bivalent nature of the binding, a scheme that has general applicability for the controlled assembly of a broad range of functional nanostructures.

关键词： directed assembly bivalent interactions DNA nanostructures 1D nanostructures

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Differential effects of short term winter thermal stress on diapausing tiger swallowtail butterflies （Papilio spp.）

引用

Insect Science 2012年第3期19卷 277-285页

作者： j. Mark Scriber Emily Maher Matthew L. Aardema Department of Entomology Michigan State University East Lansing MI McGuire Center for Lepidoptera and Biodiversity Florida Museum of Natural History University of Florida Gainesville FL Department of Ecology and Evolutionary Biology Princeton University Princeton N J USA

It is generally thought that insects inhabiting lower latitudes are more severely impacted by changes in their thermal environment than are high latitude species. This is attributed to the wider range of temperatures to which high-latitude species are exposed. By contrast, low-latitude species have typically evolved in more thermally stable environments with a narrower range of temperature variation. However, deviation from this pattern can occur and here we report that under variable winter conditions a higher latitude species may be more sensitive to thermal variation than its lower latitude sister species. Using split broods, we examined the survival and adult emergence success of diapausing pupae of Papilio canadensis and P. glaucus, as well as a unique, recombinant hybrid population （＂late-flight＂） to short periods of mid-winter cold and heat stress. Our results indicate that the higher latitude, univoltine populations （P. canadensis and late-flights） exhibit lower pupal survival than the lower latitude, facultative diapauser （P. glaucus） for all mid-winter thermal stress treatments, both high and low. Size differences alone do not appear to account for the observed differences in survival or metabolic costs in these three pheno- types, as late-flight individuals are similar in size to R glaucus. We attribute the observed differences in survival and weight loss to potential metabolic differences and variation in the intensity of diapause, in addition to divergent adaptation to winter precipitation levels （e.g. snow cover） and the influences this may have on microhabitat temperature moderation.

关键词： climate change developmental threshold incipient hybrid species metabolic cost Papilionidae post-diapause delays thermal stress

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Visual ＂playback＂ of colorful signals in the field supports sensory drive for signal detectability

引用

Current Zoology 2018年第4期64卷 493-498页

作者： Alex R. GUNDERSON Leo j. FLEISHMAN Manuel LEAL Department of Integrative Biology University of California Berkeley CA 94720 USA Department of Biology Union College Schenectady NY 12308 USA Division of Biological Sciences University of Missouri 105 Tucker Hall Columbia MO 65211 USA

Colorful visual signals are important systems for investigating the effects of signaling environ ments and receiver physiology on signal evolution as predicted by the sensory drive hypothesis. Support for the sensory drive hypothesis on color signal evolution is mostly based on document ing correlations between the properties of signals and habitat conditions under which the signals are given （i.e., a correlational approach） and less commonly on the use of mathematical models that integrate representations of visual environments, signal properties, and sensory systems （i.e., a functional approach）. here, we used an experimental approach in the field to evaluate signal efficacy of colorful lizard throat fans called dewlaps that show geographic variation in the lizard Anolis cristatellus. We used a remote controlled apparatus to display ＂fake dewlaps＂ to wild lizards to test for adaptive divergence in dewlap brightness （i.e., perceived intensity） among populations in situ. We found evidence of local adaptation in dewlap brightness consistent with the sensory drive hypothesis. Specifically, dewlaps that had the brightness characteristics of local lizards were more likely to be detected than those with the brightness characteristics of nonlocal lizards. Our findings indicate that simplified mathematical representations of visual environments may allow robust estimates of relative detectability or conspicuousness in natural habitats. We have shown the feasibility of evaluating color signal efficacy experimentally under natural conditions and dem onstrate the potential advantages of presenting isolated components of signals to an intended re ceiver to measure their contribution to signal function.

关键词： Anolis color signal sensory drive signal evolution

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Dewlap size in male water anoles associates with consistent inter-individual variation in boldness

引用

Current Zoology 2019年第2期65卷 189-195页

作者： Breanna j. PUTMAN Kylee R. AZURE Lindsey SWIERK Department of Ecology and Evolutionary Biology University of California Los Angeles CA 90095-1606 USA Section of Herpetology and Urban Nature Research Center Natural History Museum of Los Angeles County Los Angeles CA 90007 USA Environmental Science Department Aaniiih Nakoda College Harlem MT 59526 USA dSchool of Forestry and Environmental Studies Yale University New Haven CT 06511 USA

Male sexually selected signals can indicate competitive ability by honestly signaling fitnessrelevant traits such as condition or performance. However, behavior can also influence contest outcomes;in particular, boldness often predicts dominance rank and mating success. here, we sought to determi ne whether male ornament size is associated with consiste nt in dividual differences in boldness in water anoles Anol is aquaticus. We measured the relative size of the dewlap, a flap of skin under the chin that is a sexually selected ornament in Anolis lizards, and tested for associations with responses to a novel and potentially risky environment: time to emerge from a refuge into an arena and number of head sea ns post-emergence. We found that in dividuals con siste ntly differed in both time to emerge and head sea nning (i.e., in dividual resp on ses were repeatable), and that dewlap size was negatively related to nu mber of head sea ns. This suggests that orname nt size could indicate male boldness if seanning represents antipredator vigilance. We found that males that had larger relative dewlaps were also in better body condition, but boldness (i.e., head scann ing) was not related to condition. Lastly, we found con siste nt d iff ere nces in behavior betwee n trials, showing that anoles were becoming habituated or sensitized to the testing arena. Overall, our study shows that in additi on to indicating con dition and perform a nee, dewlap size could also honestly indicate male boldness in Anolis lizards.

关键词： Anolis aquaticus behavioral syndrome mating success personality signal sexual selection temperament

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

On a general theory for compressing process and aeroacoustics:linear analysis

引用

Acta Mechanica Sinica 2010年第3期26卷 355-364页

作者： E .Mao Y. P. Shi j. Z. Wu State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University 100871 Beijing China University of Tennessee Space Institute Tullahoma TN 37388 USA

Of the three mutually coupled fundamental processes （shearing, compressing, and thermal） in a general fluid motion, only the general formulation for the compress- ing process and a subprocess of it, the subj.ct of aeroacous- tics, as well as their physical coupling with shearing and thermal processes, have so far not reached a consensus. This situation has caused difficulties for various in-depth complex multiprocess flow diagnosis, optimal configuration design, and flow/noise control. As the first step toward the desired formulation in fully nonlinear regime, this paper employs the operator factorization method to revisit the analytic linear theories of the fundamental processes and their decomposi- tion, especially the further splitting of compressing process into acoustic and entropy modes, developed in 1940s-1980s. The flow treated here is small disturbances of a compressible, viscous, and heat-conducting polytropic gas in an unbounded domain with arbitrary source of mass, external body force, and heat addition. Previous results are thereby revised and extended to a complete and unified theory. The theory pro- vides a necessary basis and valuable guidance for developing corresponding nonlinear theory by clarifying certain basic issues, such as the proper choice of characteristic variables of compressing process and the feature of their governing equations.

关键词： Longitudinal (compressing) processTransversal (shearing) process Acoustic mode Entropy mode Aeroacoustics

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Condition-dependence and sexual ornamentation： Effects of immune challenges on a highly sexually dimorphic grasshopper

引用

Insect Science 2018年第4期25卷 617-630页

作者： j. Pablo Valverde Hendrik Eggert j.achim Kurtz Holger Schielzeth Department of Evolutionary Biology Bielefeld University Bielefeld Germany Institute for Evolution and Biodiversity Westfalische Wilhelms-Universitat Munster Munster Germany and 3 Department of Population Ecology Institute of Ecology Friedrich Schiller University Jena Germany Department of Population Ecology Institute of Ecology Friedrich Schiller University Jena Germany

Sexual ornaments contribute substantially to phenotypic diversity and it is particularly relevant to understand their evolution. Ornaments can assume the function of signals-of-quality that the choosy sex uses to evaluate potential mating partners. Often there are no obvious direct benefits and investment into mate choice is primarily rewarded by beneficial alleles that are inherited to the offspring. Inter-sexual communication via sexual ornaments requires honesty of the sexual signal, yet the question of what maintains honesty remains only partially solved. One solution is that honesty is maintained by trait expression being dependent on individual condition, since condition-dependent trait expression offers an effectively inexhaustible source of genetic variability. here we test in the highly sexually dimorphic club-legged grasshopper Gomphocerus sibiricus if putative sexual ornaments, in particular the striking front-leg clubs, are more strongly affected by a lipopolysaccharide （LPS） immune challenge than putatively not sexually selected traits. Our results show overall little condition-dependent expression of morphological and song traits, with sexually selected traits exhibiting effects comparable to nonsexually selected traits （with the possible exception of stridulatory file length and syllable-to-pause ratio in advertisement songs）. Interestingly, field observations of individuals of lethally parasitized individuals suggest that a very strong environmental challenge can specifically affect the expression of the front-leg clubs. The presence of 1% of males in natural populations with missing or heavily deformed clubs plus 5% with minor club deformations furthermore indicate that there are risks associated with club development during final ecdysis and this might act as a filter against deleterious alleles.

关键词： Acrididae honest signaling Orthoptera phenotypic plasticity sexualselection

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

柔性直流输电并网风电厂的低电压穿越能力改进(英文)

引用

电力系统自动化 2015年第3期39卷 14-22页

作者： Ranj.n SHARMA Qiuwei WU Seung Tae cha Kim Hφj.j.NSEN Tony Wederberg RASMUSSEN j.cob ΦSTERGAARD Siemens Wind Power A/S Center for Electric Power and Energy Department of Electrical EngineeringTechnical University

To achieve active control of the AC voltage magnitude of wind power plant(WPP)collector network and improve the fault ride-through(FRT)capability,an FRT scheme based on feed forward DC voltage control is presented for voltage source converter-high voltage direct current(VSC-HVDC)connected offshore *** steady state operation,an open loop AC voltage control is implemented at the WPP-side VSC of the HVDC system so that any possible control interactions between WPP-side VSC and VSC of wind turbine are *** during any grid fault,a dynamic AC voltage reference is made according to both the DC voltage error and AC active current from the WPP collector system,thus ensuring fast and robust FRT of the VSC-HVDC-connected offshore *** the unbalanced fault condition in the host power system,the resulting oscillatory DC voltage is directly used in the VSC AC voltage controller at the WPP side so that the WPP collector system voltage also reflects the unbalance in the main *** domain simulations are performed to verify the efficacy of the FRT scheme based on the proposed feed forward DC voltage *** results show satisfactory FRT responses of the VSC-HVDC-connected offshore WPP under balanced and unbalanced faults in the host power system,as is shown under a serious fault in the WPP collector network.

关键词：电网故障连接海上能力直流输电系统电压控制器不平衡故障电厂

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：