检索结果-南通市图书馆

Exploring ancestral phenotypes and evolutionary development of the mammalian middle ear based on Early Cretaceous Jehol mammals

在线全文

学校读者我要写书评

暂无评论

National Science Review 2021年第5期8卷 57-66页

作者： Fangyuan Mao Cunyu Liu Morgan Hill Chase Andrew k.smith Jin Meng key Laboratory of Evolutionary Systematics of Vertebrates Institute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of Sciences CAS Center for Excellence in Life and Paleoenvironment Division of Paleontology American Museum of Natural History Beipiao Pterosaur Museum of China 5. Microscopy and Imaging Facility American Museum of Natural History Earth and Environmental Sciences Graduate CenterCity University of New York

We report a new Cretaceous multituberculate mammal with 3 D auditory bones preserved. Along with other fossil and extant mammals, the unequivocal auditory bones display features potentially representing ancestral phenotypes of the mammalian middle ear. These phenotypes show that the ectotympanic and the malleus-incus complex changed notably during their retreating from the dentary at various evolutionary stages and suggest convergent evolution of some features to extant mammals. In contrast, the incudomalleolar joint was conservative in having a braced hinge configuration, which narrows the morphological gap between the quadroarticular jaw joint of non-mammalian cynodonts and the incudomalleolar articulations of extant mammals. The saddle-shaped and abutting malleus-incus complexes in therians and monotremes, respectively, could have evolved from the braced hinge joint *** evolutionary changes recorded in the Mesozoic mammals are largely consistent with the middle ear morphogenesis during the ontogeny of extant mammals, supporting the relation between evolution and development.

关键词： Cretaceous Jehol Biota malleus-incus ectotympanic mammal evolution

Leaf/shoot level ecophysiology in two broadleaf and two needle-leaf species under representative cloud regimes at alpine treeline

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Plant Ecology 2016年第6期9卷 762-772页

作者： Adriana Sanchez Nicole M.Hughes William k.smith Programa de Biología Universidad del RosarioCarrera 24 No.63C-69BogotáDC 110011Colombia Department of Biology Wake Forest University136 Winston HallWinston-SalemNC 27106USA Department of Biology High Point UniversityUniversity Station 3591High PointNC 27262USA

Aims The effects of clouds are now recognized as critically important to the understanding of climate change impacts on ***,few studies have focused specifically on the ecophysiological responses of plants to *** continental mountain ranges are characterized by common convective cloud formation in the afternoons,yet little is known regarding this influence on plant water and carbon *** we compare the ecophysiology of two contrasting,yet ubiquitous growth forms,needle-leaf and broadleaf,under representative cloud regimes of the Snowy Range,Medicine Bow Mountains,southeastern Wyoming,*** Photosynthetic gas exchange,water use efficiency,xylem water potentials and micrometeorological data were measured on representative clear,overcast and partly cloudy days during the summers of 2012 and 2013 for two indigenous broadleaf(Caltha leptosepala and Arnica parryi)and two needle-leaf species(Picea engelmannii and Abies lasiocarpa)that co-occur *** Findings Reductions in sunlight with cloud cover resulted in more dramatic declines in photosynthesis for the two broadleaf species(ca.50-70%reduction)versus the two conifers(no significant difference).In addition,the presence of clouds corresponded with lower leaf conductance,transpiration and plant water status in all ***,the more constant photosynthesis in conifers under all cloud conditions,coupled with reduced transpiration,resulted in greater water use efficiency(ca.25%higher)than the broadleaf *** differences appear to implicate the potential importance of natural cloud patterns in the adaptive ecophysiology of these two contrasting,but common,plant growth forms.

关键词： gas exchange light response curves water use efficiency xylem water potential

Minimal conceptual models for tropical cyclone intensification

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Tropical Cyclone Research and Review 2022年第2期11卷 61-75页

作者： Michael T.Montgomery Roger k.smith Department of Meteorology Naval Postgraduate SchoolMontereyCAUSA Meteorological Institute Ludwig-Maximilians UniversityMunichGermany

We examine a hierarchy of minimal conceptual models for tropical cyclone *** models are framed mostly in terms of axisymmetric balance *** the first set of models,the heating rate is prescribed in such a way to mimic a deep overturning circulation with convergence in the lower troposphere and divergence in the upper troposphere,characteristic of a region of deep moist *** the second set,the heating rate is related explicitly to the latent heat release of ascending air *** release of latent heat markedly reduces the local static stability of ascending air,raising two possibilities in the balance *** first possibility is that the effective static stability and the related discriminant in the Eliassen equation for the overturning circulation in saturated air,although small,remains positive so the Eliassen equation is globally *** second possibility,the more likely one during vortex intensification,is that the effective static stability in saturated air is negative and the Eliassen equation becomes locally *** models help to understand the differences between the early Ooyama models of 1968 and 1969,the Emanuel,1989 model,and the later Emanuel models of 1995,1997 and *** provide insight also into the popular explanation of the WISHE feedback mechanism for tropical cyclone *** implications for recent work are discussed.

关键词： Tropical cyclone intensification Conventional spin-up mechanism Minimal models Nonlinear boundary layer spin-up mechanism WISHE feedback Mechanism

An Analytical Assessment and Examination of Supervised Tree Based Classifier in Intrusion Detection System

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

An Analytical Assessment and Examination of Supervised Tree ...

作者： Lavocier k.smith,Jr. 湖南大学

学位级别：硕士

目前网络安全越来越受到关注,尤其是由于数据泄露造成的安全威胁问题,使得网络安全成为计算机科学领域的一个重要的研究领域。为了处理例如数据被捕获以及随之非法侵入系统等情况,网络安全工作人员已经采取了一些方法来帮助预防和消除... 详细信息

目前网络安全越来越受到关注,尤其是由于数据泄露造成的安全威胁问题,使得网络安全成为计算机科学领域的一个重要的研究领域。为了处理例如数据被捕获以及随之非法侵入系统等情况,网络安全工作人员已经采取了一些方法来帮助预防和消除这些威胁,其中许多方法使用了机器学习技术的方法。这种方法是本论文的研究所提倡的方法,它是确定网络入侵检测最可靠的方法之一。随着互联网时代的引入和许多用户可用资源的大量增加,数据泄露风险已日益增加,并且正成为影响计算机用户安全的一个迫切并且极具挑战性问题因此。由于互联网上入侵事件的增加,目前开发了许多互联网入侵检测系统来来防止互联网攻击。数据挖掘,模式识别和分类方法都被用于将网络事件分类为正常或异常网络事件。本论文中在寻求比较和评估入侵能力时,引入不同的基于树的分类算法,其具有在监督方法下对入侵检测系统中的网络事件进行分类的能力,该监督方法是机器学习分类过程的三种类型之一。论文的分析使用了以下基于树的分类器:C4.5,ADTree,RandomTree和RandomForest。在预处理阶段将应用一种称为离散化的监督过滤器,数据挖掘中的离散化是将数量型数据转换为质量型数据的过程。论文中采用了两种不同的特征选择方法,即:一致性子集评估和相关特征子集评估,用于论文对数据集进行降维。为了展示提出的评估方法的性能,本文中的实验是在NSL-kDD数据集上进行。同时为了减少这个数据集的一些元素的属性以提高分析的准确性,论文中使用了Random Tree模型,C4.5,ADTree和Random Forest这些入侵检测系统性能的方法。在网络入侵检测研究中,发现攻击的一种策略是监控网络的异常活动:通常使用机器学习工具,来确定偏离于从良性网络流量中学习到的正常模式。然而,广泛的学术研究发现这种系统实际部署方面有显著的差距:与其它入侵检测方法相比,机器学习很少部署于现实环境。检查网络入侵检测问题与机器学习定期发现更多成功的其他领域之间的差异,他们的性能和减少虚假警报的能力。本文的主要工作是指出发现攻击流量与其它应用程序完全不同,这使得通过使用机器学习方法来降低报警率变得非常困难。本文通过识别网络入侵检测的挑战来支持这一论点,并提供一套旨在加强未来异常检测研究的方法。机器学习工具的优势在于找到类似于以前所看到的活动,而不需要将前面的活动精确描述。此外,本文还给出开源软件的特性与机器学习的要求之间的不同。这些要求包括:非常高的错误代价;缺乏训练数据;结果与其操作解释之间的语义差距;输入数据的巨大差异;进行健全评估的难度。为了解决这些问题,本文认为对于任何有效的部署来说,深入了解系统的能力和局限性是关键的,而不是将系统视为一个黑匣子。机器学习是一个适合于入侵检测的工具,然而使用它需要注意:更清晰的可以定义其运行的上下文;越了解检测过程的语义,系统的操作性就越强。入侵检测是网络安全的一个主要研究问题,其目的是识别不寻常的访问或攻击来保护内部网络。入侵检测系统已经使用过各种机器学习技术。但是,目前还没有分析使用机器学习技术来解决入侵检测问题的现状研究。相关研究通过比较分类器设计和所使用的数据集。本文展示和讨论通过机器学习开发入侵检测系统目前的成果和局限性,还提供了一些未来的研究方向。防火墙通过阻止对不需要的端口的访问来控制TCP/IP网络流量。但是,它会打开应用程序使用的端口,例如端口 80用于HTTP流量。因此,所有的HTTP攻击都不会被防火墙所阻止。类似地,防病毒系统非常适合检测病毒,但时间已经证明,它们无法保护系统免受恶意软件(如广告软件或间谍软件)的侵扰。密码肯定会在安全系统中提供基本构件,但容易发生攻击;在最坏的情况下,他们可能手动或电子窃取,甚至被轻易猜到。因此,具有基本的安全性只会给你一种安全的错觉,而不是实际的安全。现代攻击者是通过使用不同工具来利用软件漏洞的专家,并设计出有效方法来攻破网络以实现其目标。为了处理智能攻击,需要一个更加智能的安全机制。IDS或IPS(入侵保护服务)是包含这些要求的解决方案。重要的是,网络中的安全性与网络中最不安全的基础架构组件一样好。例如,如果桌面未修补,则可能会成为病毒,木马和恶意软件隐藏的潜在节点。因此,安装IDS,配置并使用它来查看企业网络中的所有网段,从面向Internet的DMZ到内部LAN是非常重要的。入侵检测是计算机安全的核心技术之一。入侵检测的目标是可以识别网络流量,操作系统事件或日志条目中的恶意行为。大多数当前入侵检测系统(IDS)遵循基于签名的方法,类似于病毒扫描器,检测到匹配的被称为“签名”的特定预定义模式的事件。基于签名的IDS的主要限制是不能识别新的攻击,甚至是已知模式的微小变化。此外,维护签名数据库会产生较大的管理开销。监督学习可用于自动生成检测器,而无需手动删除和更

关键词：特征选择入侵系统检测随机树模型分类离散

Application of the rotating-convection paradigm for tropical cyclones to interpreting medicanes:An example

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

Tropical Cyclone Research and Review 2022年第3期11卷 131-145页

作者： Gerard kilroy Hongyan Zhu Minhee Chang Roger k.smith Meteorological Institute Ludwig-Maximilians UniversityMunichGermany Research Science and InnovationBureau of MeteorologyMelbourneAustralia School of Earth and Environmental Sciences Seoul National UniversitySeoulSouth Korea

The rotating-convection paradigm for tropical cyclone behaviour is shown to provide an attractive and consistent framework for interpreting the dynamics of formation and intensification of at least some *** ideas are illustrated by a case study of the medicane that formed over the eastern Mediterranean in mid-December *** case study is based on analyses of data from the European Centre for Medium Range Weather Forecasts(ECMWF),imagery from the European geostationary meteorological satellite,Meteosat Second Generation,and output from a convection permitting numerical simulation of the event using the United kingdom(Uk)Met Office regional model with the RAL2 physics *** of the currently widely accepted interpretation of medicanes in terms of the so-called Wind-Induced Surface Heat Exchange(WISHE)intensification mechanism are discussed.

关键词： Tropical cyclone Hurricane Typhoon Deep convection Medicane

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

校园欺凌的跨文化差异问题:特征与干预

心理发展与教育 2023年第4期39卷 599-608页

作者： Peter k.smith 山东师范大学心理学院济南250014 英国伦敦大学金史密斯学院心理学系英国伦敦SE146NW

校园欺凌是全世界关注的重要公共健康问题,会给所有的卷入者造成消极影响。早期校园欺凌研究主要集中在欧洲,此后逐步拓展到北美和日本。进入21世纪,校园欺凌研究遍布世界各国,尤其是中国校园欺凌研究的增速非常快。许多大型调查项目,如... 详细信息

校园欺凌是全世界关注的重要公共健康问题,会给所有的卷入者造成消极影响。早期校园欺凌研究主要集中在欧洲,此后逐步拓展到北美和日本。进入21世纪,校园欺凌研究遍布世界各国,尤其是中国校园欺凌研究的增速非常快。许多大型调查项目,如HBSC、GSHS、TIMSS、PISA和EUkO等先后报告了不同国家校园欺凌的发生率、严重程度与基本特征。不同的文化中,“欺凌”内涵与特征存在许多相似之处,同时也存在一些值得关注的差异。本文依据Bronfenbrenner的社会生态模型和EU kids Online的五因素模型作为框架,总结了校园欺凌在不同国家的异同之处,梳理了跨国比较研究和比较不同国家欺凌发生率时所面临的挑战,如何解释跨国比较时出现的差异,以及对于欺凌干预的启示。

关键词：欺凌跨文化差异特征干预

Preliminary age-based life history characteristics of the dogtooth tuna,Gymnosarda unicolor(Ruppell,1838),in the southwest Pacific Ocean

在线全文

学校读者我要写书评

暂无评论

Aquaculture and Fisheries 2023年第3期8卷 323-331页

作者： David J.Welch Adam k.smith kyne krusic-Golub Sandra Erdmann Stephen J.Newman C_(2)O Fisheries PO Box 3041CairnsQueensland4870Australia Centre for Sustainable Tropical Fisheries and Aquaculture College of Science and EngineeringJames Cook UniversityTownsville4811Australia Reef Ecologic TownsvilleQueensland4811Australia Fish Ageing Services Pty.Ltd. QueenscliffVictoria3225Australia Western Australian Fisheries and Marine Research Laboratories Department of Primary Industries and Regional DevelopmentGovernment of Western AustraliaNorth BeachWestern Australia6020Australia

Dogtooth tuna,Gymnosarda unicolor were sampled off the east coast of Australia(southwest Pacific Ocean)from 2007 to *** were determined by examining thin transverse sections of their sagittal otoliths and were based on counts of alternating opaque and translucent zones(annual growth increments).Growth was rapid during the first year of life,after which growth in length was much *** of the constrained von Bertalanffy growth function(fork length-at-age)were L∞=1164.77(mm,FL)and k=0.44 year^(-1).Preliminary estimates of longevity indicate a maximum observed age of at least 20 *** was a high degree of variation in the observed length and age of sexual maturity for *** this variation,the size at 50%maturity for female *** estimated in this study was 713 mm FL(<2 years of age).The diet of *** is very broad and covers a range of fish *** life history characteristics of *** overall,indicate that this species may be somewhat resilient to ***,reports of localised depletions,in association with heavy targeting by sports fishers,low effective population sizes and patchy recruitment indicate that this species is particularly vulnerable to overfishing.

关键词： Otoliths Age Life history Pacific ocean Diet Fisheries management

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

饲料中霉菌毒素对家禽免疫机能的危害

中国家禽 2008年第16期30卷 35-37页

作者： Trevor k.smith 加拿大圭尔夫大学

霉菌毒素是由真菌（霉菌）产生的一系列化学性质各异的化合物，是家禽饲料中常见的污染物。对家禽生产造成经济损失的霉菌毒素有：黄曲霉毒素，赭曲霉毒素，单端孢菌毒素，玉米赤霉烯酮和烟曲霉毒素。霉菌毒素的有害影响主要通过四个机... 详细信息

霉菌毒素是由真菌（霉菌）产生的一系列化学性质各异的化合物，是家禽饲料中常见的污染物。对家禽生产造成经济损失的霉菌毒素有：黄曲霉毒素，赭曲霉毒素，单端孢菌毒素，玉米赤霉烯酮和烟曲霉毒素。霉菌毒素的有害影响主要通过四个机制：①降低采食量；②减少营养吸收；③内分泌影响以及；④抑制免疫机能。在这些不同的机制中，霉菌毒素抑制免疫机能对家禽生产造成的经济损失最大。

关键词：霉菌毒素免疫机能家禽饲料危害玉米赤霉烯酮经济损失家禽生产黄曲霉毒素

家禽霉菌毒素中毒症的病因学和预防方面的新观点

在线全文

学校读者我要写书评

暂无评论

中国家禽 2005年第9期27卷 30-32页

作者： Trevor k.smith 加拿大圭尔夫大学动物和家禽科学系