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Response of endemic afroalpine rodents to the removal of livestock grazing pressure

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current Zoology 2011年第6期57卷 741-750页

作者： Flavie VIAL david w. MAcDONALD Daniel T. HAYDON Boyd Orr centre for Population and Ecosystem Health Institute of Biodiversity Animal Health and Comparative Medicine College of Medical Veterinary and Life Sciences University of Glasgow Glasgow G12 8QQ UK. wildlife conservation Research Unit Zoology Department University of Oxford The Recanati-Kaplan Centre Tubney House Tubney OX13 5QL UK.

The Bale Mountains of Ethiopia represent the world＇s largest continuous extent of afroalpine habitat. with a peak combined density of over 8000 individuals/km2, the endemic giant mole rat Tachyoryctes macrocephalus, Blick＇s grass rat Arvi- canthis blicki and the brush-furred mouse Lophuromys melanonyx are the dominant wild herbivores within this ecosystem and may be affected by the presence of high densities of domestic livestock. The purpose of this study was to establish whether these endemic rodent populations could respond to the removal of grazing pressure inside three 0.25 hectare livestock exclosures （paired with grazed control plots） and to determine whether such response was mediated through concomitant changes in the vegetation structure. we hypothesised that livestock grazing negatively affects endemic rodent populations through competition or increased predation risk and we predicted an increase in rodent biomass following the removal of grazing pressure. we found no evidence of rodent populations responding to the removal of livestock after fourteen months. The short-term nature of the ex- perimental design, environmental fluctuations and the ecosystem＇s inherent stochasticity may explain the apparent lack of a sig- nificant response. However, while this study is inconclusive, it emphasises the need for more long-term experimental investiga- tions to assess the effects of domestic grazers on vegetation and on dependent communities. The effects of rapidly increasing livestock numbers in the Bale Mountains will require continued close monitoring of vegetation and endemic animal communities as the afroalpine is altered by external biotic and abiotic forces .

关键词： Afroalpine Bale Mountains Exclosures Livestock grazing Murid rodents

Positron imaging systems for studying particulate, granular and multiphase flows

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Particuology 2012年第2期10卷 146-153页

作者： Thomas w.Leadbeater david J.Parker Joseph Gargiuli Positron Imaging centre University of BirminghamEdgbastonBirmingham B152TTUKa

The University of Birmingham has pioneered and adapted the use of the medical imaging technique known as positron emission tomography （PET） to the study of particulate, granular and multiphase flows in industrial and physical processes, This paper provides a review of the PET and complimentary positron emission particle tracking （PEPT） techniques and details their application to the study of particulate sys- tems, The current state of the art, recent developments and example results from many of the applications to which these techniques have been applied are highlighted.

关键词： Positron emission particle tracking (PEPT)Particle dynamicsMulti-phase flow measurement

creep-fatigue lives prediction and sensitivity study of 316H at 550 ℃

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Acta Metallurgica Sinica(English Letters) 2011年第2期24卷 132-140页

作者： Zhichao FAN david J Smith Xuedong cHEN Mike w Spindler Hefei General Machinery Research Institute Hefei 23-0031 China University of Bristol Bristol BS8 1TR UK British Energy Gloucester GL4 3RS UK

In Volume 2/3 of R5 ＂An assessment procedure for the high temperature response of structures＂, the strain based ductility exhaustion method is suggested to calculate the creep damage of stress concentration region, which involves description of creep dwell initial stress, stress drop and creep ductility. considering lots of uncertainty existed in these assessment, some sensitivity analysis is required in R5 procedure to ensure the conservatism of assessment results. In this paper, laboratory creep-fatigue test data of 316H at 550 ℃ with different loading conditions are selected as a special case to investigate whether the basic R5 approach is conservative, and the different material data combinations of cyclic stress-strain, creep deformation and creep ductility are used to identify those significant parameters affecting the assessment results. The analytical results indicate that the creep deformation model and creep ductility data are more significant to the results comparing with cyclic stress-strain data. If the upper bound of creep deformation law and lower bound of creep ductility data are used to predict their creep-fatigue lives, the degree of conservatism can be as large as a factor of -300, but if the modified creep deformation model and cast specific ductility data are used, very well prediction results can be gained within a factor of ±2.0 although there is slight non-conservatism.

关键词： creep Fatigue Damage Life prediction Sensitivity study

Superhydrophobic modification of cellulose and cotton textiles:Methodologies and applications

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Journal of Bioresources and Bioproducts 2020年第1期5卷 1-15页

作者： david w.wei Haiying wei Alec c.Gauthier Junlong Song Yongcan Jin Huining Xiao Department of chemical Engineering University of New BrunswickFrederictonNB E3B 5A3Canada Joint International Research Lab of Lignocellulosic Functional Materials and Provincial Key Lab of Pulp and Paper Sci&Tech.Nanjing Forestry University Nanjing 210037China

Superhydrophobic cellulose-based products have immense potential in many industries where plastics and other polymers with hydrophobic properties are *** cellulose-based plastic is inherently biodegradable,renewable and *** a suitable replace-ment of plastics is highly desired since plastics has become an environmental *** its inherent hydrophilicity,cellulose has unparalleled advantages as a substrate for the produc-tion of superhydrophobic materials which has been widely used in self-cleaning,self-healing,oil and water separation,electromagnetic interference shielding,*** review includes a compre-hensive survey of the progress achieved so far in the production of super-hydrophobic materials based on cellulose and fiber *** methodologies and applications of superhydrophobic-modified cellulose and fiber networks are ***,presented herein is targeting on summarizing some of the aspects that are critical to advance this evolving field of science which may provide new ideas for the developing and exploring of superhydrophobic and green-based materials.

关键词： cellulose Superhydrophobic modification cotton textile Methodologies Applications

An investigation into the potential of Gabor wavelet features for scene classification in wild blueberry fields

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Artificial Intelligence in Agriculture 2021年第1期5卷 72-81页

作者： Gashaw Ayalew Qamar Uz Zaman Arnold w.Schumann david c.Percival Young Ki chang Independent Researcher ThoroldON L2V 1Z8Canada Engineering Department Dalhousie University Faculty of AgricultureTruroNS B2N 5E3Canada citrus Research and Education centre University of FloridaLake AlfredFL33850USA Plant Animal and Environmental Sciences DepartmentDalhousie University Faculty of AgricultureTruroNS B2N 5E3Canada

A Gabor wavelets based technique was investigated as a potential tool for scene classification(into one of bare patch,plant,or weed)for its ultimate utility in site-specific application of agrochemicals inwild blueberry *** were gathered from five sites located in central Nova Scotia,*** wavelet features extracted from these images were used to classify scenes according to visually determined classes using step-wise linear discriminant *** individual fields,classification accuracy attained ranged between 87.9%and 98.3%;selected Gabor features ranged between 27 and 72;contextual accuracy for herbicide ranged between 67.5%and 96.7%,and contextual accuracy for fertilizer ranged between 63.6%and 97.1%.The pooled scenes yielded a classification accuracy of 81.4%,and contextual accuracy figures of 61.1%and 73.1%for herbicide and fertilizer,respectively,with selected Gabor features of *** based on LDA coefficients from the pooled scenes could help avoid the need to re-calibrate for each field,whereas those based on individual field LDA coefficients could improve accuracy,hence enable saving on expensive agrochemicals.

关键词： wavelet transforms wild blueberry computer vision Machine learning Discriminant analysis Precision agriculture

Origins of perturbations in dayside equatorial ground magnetograms

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Earth and Planetary Physics 2024年第1期8卷 215-221页

作者： Syau-Yun w.Hsieh david G.Sibeck The Johns Hopkins University Applied Physics Laboratory LaurelMarylandUSA NASA Goddard Space Flight center GreenbeltMarylandUSA

To determine the cause(s)of perturbations seen in dayside equatorial ground magnetograms,we conducted a systematic survey of simultaneous ground-based and geosynchronous satellite-based observations during the 90-day period from December 1,2020 to February 28,*** examined Huancayo ground magnetometer observations from 14:00:00 to 20:00:00 UT each day,during which Huancayo passed through local *** those data we chose perturbation events selected on the basis of large(>20 nT)event amplitude and classified the selected events as responding primarily to solar wind pressure,or to variations in the north/south component of the interplanetary magnetic field(IMF Bz),or perhaps in part to *** results show that an equivalent number of events were identified for each model during this 90-day *** in the lagged solar wind dynamic pressure routinely correspond to nearly simultaneous sudden impulses recorded at both geosynchronous orbit and on the *** in IMF Bz produce erosion signatures at geosynchronous orbit and can correspond to ground events if lag times for reconnection to enhance convection in the magnetosphere are taken into account.

关键词： dayside magnetosphere dayside equatorial ionosphere geosynchronous magnetic field

Recent research on vasectomy techniques

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Asian Journal of Andrology 2003年第3期5卷 227-230页

作者： david c.Sokal clinical Research Division Family Health International Durham NC 27713 USA

Vasectomy is a commonly used, highly effective method for the control of fertility in the human male. It is almost always performed as an outpatient procedure, is safer than tubal occlusion and has few side effects. The number of people relying on vasectomy as a method of contraception varies widely from country to country. Though vasectomy is highly effective, failures may occur due to re-canalization of the vas, surgical error, anatomical variants or failure of contraception during the post-operative waiting period. One of the disadvantages of this technique is that sperm are present in the posterior end of the vas following surgery and hence patients have to use alternative methods of contraception for a waiting period of 12 weeks to 15 weeks before relying on a vasectomy for contraception. This review summarizes recent research on vasectomy conducted by Family Health International, USA.

关键词： male sterilization vasectomy treatment efficacy safety

cryogenic nanosecond and picosecond high average and peak power(HAPP) pump lasers for ultrafast applications

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High Power Laser Science and Engineering 2016年第2期4卷 37-67页

作者： david c.Brown Sten Tornegrd Joseph Kolis Snake creek Lasers LLC clemson University Department of Chemistry

Using cryogenic laser technology, it is now possible to design and demonstrate lasers that have concomitant high average and peak powers, with near-diffraction-limited beam quality. we refer to these new laser systems as HAPP lasers. In this paper, we review important laser crystal materials properties at cryogenic temperature, with an emphasis on Yb lasers, and discuss the important design considerations, including the laser-induced damage threshold, nonlinear effects and thermal effects. A comprehensive model is presented to describe diode pulsed pumping with arbitrary duration and repetition rate, and is used with the Frantz–Nodvik equation to describe, to first order, the performance of HAPP laser systems. A computer code with representative results is also described.

关键词： cryogenic lasers high-average-power lasers high-peak-power lasers ultrafast lasers Yb lasers

Subordinacy theory for extended cMV matrices

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Science china Mathematics 2022年第3期65卷 539-558页

作者： Shuzheng Guo david Damanik Darren c.Ong School of Mathematical Sciences Ocean University of ChinaQingdao 266100China Department of Mathematics Rice UniversityHoustonTX 77005USA Department of Mathematics Xiamen University MalaysiaSepangSelangor Darul Ehsan 43900Malaysia

we develop subordinacy theory for extended cantero-Moral-Velázquez(cMV) matrices,i.e.,we provide explicit supports for the singular and absolutely continuous parts of the canonical spectral measure associated with a given extended cMV matrix in terms of the presence or absence of subordinate solutions to the generalized eigenvalue *** corollaries and applications of this result are described as well.

关键词： spectral theory subordinacy theory cMV matrix unitary operator carathéodory function