地图计算机颜色模型研究     

刘书楼  陈宝雯 《地理学报》1993,48(6):535-543

地图计算机颜色模型（MCCM）研究包括实用色谱印刷色标的制定、色标的屏幕再现与印刷复原、地图设色专家系统等。通过科学实验和系统分析,本文从色度学理论上阐明了屏幕再现印刷颜色出错的原因,从方法上解决了色标再现及复原研究长期存在的技术难题,建立了地图颜色模型数据库,为地图设包标准化、规范化提供了计算机手段。  相似文献   

Age, growth and reproduction of the sand smelt Atherina boyeri Risso, 1810 in the Gomishan wetland – southeast Caspian Sea     

Rahman Patimar  Morteza Yousefi  Seyyed Morteza Hosieni 《Estuarine, Coastal and Shelf Science》2009,81(4):457-462

A total of 2256 specimens of Atherina boyeri caught in Gomishan wetland (a marsh lagoon located at the southeast Caspian Sea) during spawning season from February to August 2007 were examined for life-history attributes. The population has a 4-year life cycle. Length–weight relationship was estimated as W = 0.0053TL^3.0181 for males and W = 0.0050TL^3.063 for females, being allometrically positive for both sexes. The von Bertalanffy growth function fitted to back-calculated size at age data was: Lt = 155.17[1 − exp − 0.28(t + 0.738)] and Lt = 162.77[1 − exp − 0.27(t + 0.727)] for males and females respectively. The sex ratio was 1:1.30 in favor of females. The reproductive season, evaluated from GSI, extended from March to July, with a peak in March. The average absolute and relative fecundities were 2976 eggs and 874 eggs g⁻¹ of body weight respectively. The diameter of oocytes ranged from 0.03 to 0.20 mm with a mean value of 0.68. The life-history patterns of A. boyeri in the population under study imply that the population of this species in the southeast Caspian Sea differs markedly from those of other localities of its range distribution. The differences were thought to be due to differences in geographical locations.  相似文献   

Population ecology of the snail Melampus bidentatus in changing salt marsh landscapes          下载免费PDF全文

Roman Zajac  Erin Kelly  Danielle Perry  Ivana Espinosa 《Marine Ecology》2017,38(2)

We studied the population ecology of the snail Melampus bidentatus in relation to patch composition and landscape structure across several salt marsh systems in Connecticut, USA. These marshes have changed significantly over the past 40–50 years including loss of total area, increased areas of short Spartina alterniflora, and decreased areas and fragmentation of Spartina patens. These changes are consistent with tidal inundation patterns that indicate frequent flooding of high marsh areas. Melampus bidentatus densities were highly variable, both among different salt marsh systems and locations within specific marshes, but were generally similar among short Sp. alterniflora and Sp. patens patches within locations. Densities were lowest where the marsh was regularly inundated at high tide and only remnant Sp. patens patches remained. Almost no snails were found in bare patches. Areas that had large Sp. patens patches adjacent to short Sp. alterniflora supported the highest M. bidentatus densities. Population size‐structure varied significantly among patch types, with higher proportions of large individuals in short Sp. alterniflora and hummocked Sp. patens patches than in large and remnant Sp. patens patches. This was likely due to size‐selective predation and/or higher snail growth rates due to better food resource conditions in short Sp. alterniflora patches. Egg mass densities and the number of eggs per egg mass were highest in short Sp. alterniflora. Our results indicate that M. bidentatus is resilient to the level and patterns of salt marsh change evident at our study sites. Indeed, snail densities were significantly higher than reported in other field studies, suggesting that increased patch areas of short Sp. alterniflora and associated environmental conditions at our study sites may provide more favorable habitats than previously when marshes were dominated by extensive Sp. patens meadows. However, there may be threshold conditions that could overwhelm the ability of M. bidentatus to maintain itself within salt marsh systems where changes in hydrology, sedimentation and other factors lead to increased numbers of bare patches and ponds and loss of short Sp. alterniflora and Sp. patens. Studies of the responses of resident and transient fauna to salt marsh change are critically needed in order to better understand the implications for salt marsh ecosystem dynamics and services.  相似文献   

Adaptation of real earthquake records for their reproduction by a shaking table with limited stroke     

B Blostotsky  Y Ribakov  G Agranovich 《地震工程与工程振动(英文版)》2010,9(4):493-502

Shaking tables with moving platforms are widely used in laboratory testing of structural models and full-sized devices. In most cases, the platform’s movement should reproduce real ground acceleration records. However, the stroke of the platform, required for reproduction of real records, is usually rather large. This limitation does not allow an accurate realization of the ground motion by the shaking table. Commonly, in order to overcome this problem, original records are modified, which causes a signific...  相似文献   

基于数据再生与空间重构的岩土体变形行为预测     

董辉  杨珺博  傅鹤林  聂春龙 《岩土力学》2010,31(6):1877-1883

针对岩土体变形行为预测中观测数据的有限性以及信息的不完备性,提出以分段插值或Boostrap重采样对有限观测数据再生以增强数据细节信息,以坐标变换或状态空间重构改变时序数据的表示形式,并重写原有不显著的规律的研究方法。在深入分析方法中重采样、混沌辨识、相空间重构的嵌入维数和延迟时间等关键技术的基础上,分别采用支持向量机、径向基函数前向型神经网络（RBF）以及反馈型神经网络（Elman）,对3组不同特征工程算例的岩土体变形时序在数据再生和空间重构前后进行预测对比研究。结果表明,变形时序的数据再生与重构能够极大地扩充数据细部特征信息和凸显岩土体变形演化的本质规律,以此数据建立的SVM预测模型,其可靠性和准确性优于以原始数据SVM、RBF和Elman建模预测效果。  相似文献   

Parity and disparity between two Chama oysters: the reproductive biology of the Indo-Pacific C. pacifica Broderip,invasive to the Mediterranean Sea; and C. savignyi Lamy,indigenous to the Red Sea     

Dror Zurel  Uri Gophna  Yehuda Benayahu 《Marine Ecology》2012,33(3):261-271

The Indo-Pacific oyster Chama pacifica Broderip, 1835 (Mollusca, Bivalvia, Chamidae) is rarely found in the Northern Red Sea reefs of Eilat (Gulf of Aqaba), where it is outnumbered by its indigenous congener, Chama savignyi Lamy, 1921. The influx of Eritrean biota from the Red Sea into the Mediterranean Sea via the Suez Canal has led to the formation of massive Chama oyster beds along the Eastern Mediterranean shore. However, unlike the Northern Red Sea, the Eastern Mediterranean Chama beds are dominated by C. pacifica oysters, whereas C. savignyi is absent from this region. In an attempt to understand this difference in their respective distribution, the reproductive biology of both species was compared. Histological analysis of the male and female gonads, monitored monthly from March 2009 to August 2010 in both regions, revealed a similar reproductive cycle, comprising six stages: onset of gametogenesis, advanced gametogenesis, ripe, ready to spawn, spent and sexual rest. Female gonads demonstrated an additional, seventh stage – restoration, coinciding with inferred spawning of ripe gametes. Both species were found to be dioecious spawners, with a single, annual, temperature-dependent inferred spawning period. Chama pacifica was found to reproduce efficiently in maximal Mediterranean seawater temperatures not experienced by the Northern Red Sea Chama populations. This study demonstrates the high invasive potential of an oyster species despite its rarity in its source region.  相似文献   

日常生活视野中的旅游社区空间再生产研究——基于列斐伏尔与德塞图的理论视角   总被引：3，自引：0，他引：3  

孙九霞  周一 《地理学报》2014,69(10):1575-1589

在空间与旅游地空间的相关研究中,社区居民及其日常生活所扮演的角色未得到充分的重视.而本文试图转向微观层面,关注空间演化中居民与日常生活的力量.研究以世界文化遗产“开平碉楼与村落”核心区马降龙村为例,运用观察法与访谈法,探索由旅游发展所推动的旅游社区空间再生产的现象与特征.基于列斐伏尔的“空间三元论”与德塞图的“日常生活实践”理论,讨论在空间再生产的过程中,居民如何通过日常生活,对抗政府与景区管理主体构想的空间表征,体现具有反抗性的表征空间.研究发现,在日常生活中,反抗性的表征空间表现出嵌入、抵制、进攻性抵制、反噬、再生等形式.现阶段,低度开发水平下居民与政府及景区管理主体的对抗达到一种微妙的平衡状态.长期看来景区组织与居民角色的特性,以及对土地的掌控保障了反抗潜力的延续.而旅游社区的空间秩序最终将在所有旅游利益相关者的协商中形成.旅游发展中居民扮演的角色影响其协商能力,造成不同的行动机制与意义.旅游社区空间活力最终在多主体、多目标的空间生产过程中激发,这一过程始终展现出日常生活的创造力.  相似文献   

Sexual reproduction and short-term fitness advantage in the rotifer Brachionus calyciflorus: implications for the coexistence of sympatric clones     

孙栋  马蕊  刘玮  牛翠娟 《中国海洋湖沼学报》2013,31(5):987-993

Large numbers of rotifer eggs from sediment resting egg banks may hatch simultaneously under appropriate conditions;therefore,natural populations are likely to be multiclonal in a growing season.A recent field investigation showed that subordinate and ephemeral clones were able to establish populations in an environment with several strongly dominant clone populations.However,it was not clear how the subordinate populations maintained their growth under these conditions where the crowding signal would induce high levels of sexual reproduction in the dominant clone populations.In the present study,we conducted a continuous passage to 60 generations for new populations at three different temperatures(15°C,25°C,and 35°C).These populations emerged from resting eggs produced by a clone population.At the first,30th,and 60th generations,the populations were sampled and fitness was assayed using the life-table method.We found a significant short-term fitness advantage for populations newly emerged from resting eggs produced by a clone population of the rotifer Brachionus calyciflorus,followed by a significant decrease in relative fitness with long-term continuous passage.Our results suggested that the early shortterm fitness advantage was important for later-hatched and subordinate clone populations in an environment with multiple sympatric clones.The early short-term fitness might also promote the coexistence of sympatric clones because it could help to offset the cost of early sexual reproduction.  相似文献   

Abundance,breeding and growth of the ocypodid crab Dotilla myctiroides (Milne-Edwards) on a West Malaysian beach     

A.J. Hails  S. Yaziz 《Estuarine, Coastal and Shelf Science》1982,15(2):229-239

The ocypodid crab, Dotilla myctiroides, was studied on the south-west coast of peninsular Malaysia. The mean numbers and biomass over a year along a transect from high to low water ranged from 37·5 to 579 crabs m^?2 and from 2·22 to 50·79 g m^?2 (wet weight) respectively. Berried females were found in all months of the year but two peaks of activity were apparent, from November to February and May to July. It is suggested that this may be related to changes in food abundance associated with the effects of monsoon winds on sea currents. Laboratory growth studies indicated that maximum life span was approximately 13 months (from first crab stage) for males and 10 months for females. Growth rate decreased with increasing size of crab. Egg number increased with size of female.  相似文献   

‘Selling Our Own Skin:’ Social dispossession through microcredit in rural Bangladesh     

《Geoforum》2016

In this paper, I articulate a notion of ‘social dispossession,’ an optic that extends current theorizing on agrarian dispossession into the realm of social reproduction, by examining the testimonies of microcredit borrowers in rural Bangladesh. In recent years, research on microcredit has highlighted new forms of subject-making employed by microcredit and other NGO entrepreneurship development programs. These developments have received insufficient attention in scholarship on agrarian change, both globally and in specific places. I correct this by arguing that microcredit drives social dispossession through three specific mechanisms: the confiscation of assets necessary to social reproduction (as well as to production); the construction of debt relations within a community which reshape what reproduction can look like; and the re-configuration of women’s social status and subjectivities in relation to their communities.  相似文献