期刊文献+
共找到2,643篇文章
< 1 2 133 >
每页显示 20 50 100
Diversity of Orchids in Terms of Their Distribution, Uses and Conservation in Annapurna Conservation Area of Nepal
1
作者 Babu Lal Tiruwa Basu Dev Neupane +2 位作者 Rabin Kadariya Chiranjibi Prasad Pokheral Bijaya Pant 《American Journal of Plant Sciences》 CAS 2024年第6期422-440,共19页
The Annapurna Conservation Area (ACA), the first conservation area and the largest protected area (PA) in Nepal, is incredibly rich in biodiversity. Notwithstanding this, orchids in the ACA have not been explored enou... The Annapurna Conservation Area (ACA), the first conservation area and the largest protected area (PA) in Nepal, is incredibly rich in biodiversity. Notwithstanding this, orchids in the ACA have not been explored enough yet thus making the need for ambitious research to be carried out. Previous study only included 81 species of orchids within ACA. This study aims to update the record of species and genera richness in the ACA. In total 198 species of orchids, belonging to 67 genera (40% and 62% of the total recorded orchid species and genera in Nepal) has been recorded in ACA. This represents an increase of 144% in species and 56% in genera over the previous data. Out of the 198 species, 99 were epiphytes, 6 were holomycotrophic and 93 were terrestrial. Among the 67 genera, Bulbophyllum (17) species were dominant, followed by Dendrobium (16), Herminium (10), Coelogyne, Plantanthera (9 each), Eria, Habenaria, Oberonia (8 each), Calanthe (7), and Liparis (6). Fifty-six species were found to be ornamentally significant and 85 species medicinally significant. 展开更多
关键词 ORCHIDS Annapurna Conservation Area diversITY distribution USES
下载PDF
Diversity, Abundance and Distribution Patterns of Epibenthic Echinoderms in Dungonab Bay, Red Sea, Sudan
2
作者 Abdelmoneim Karamalla Gaiballa 《Open Journal of Ecology》 2024年第4期366-380,共15页
The abundance, distribution and diversity of epibenthic echinoderm were investigated at Dungonab Bay in the Red Sea coastal water of the Sudan. Four permanent line transects were chosen. Eight (30 × 2) square met... The abundance, distribution and diversity of epibenthic echinoderm were investigated at Dungonab Bay in the Red Sea coastal water of the Sudan. Four permanent line transects were chosen. Eight (30 × 2) square metre belt transects along each permanent line transect at 20 metre intervals were used to collect data. The data were subjected to univariate and multivariate analyses. Spatial variations of epibenthic echinoderm abundance were assessed with one-way analysis of variance. Hierarchical agglomerative clustering was used to identify and illustrate the similarities in echinoderm abundance between line transects and between belt transects. Indices of richness (d), diversity (H'), evenness (J') and dominance (C) were used to explain the diversity of epibenthic echinoderm species. The distribution pattern of each echinoderm species was determined in each permanent line transect. A total of 986 individuals were recorded within sixteen species of epibenthic echinoderms in the four line transects. Holothuriidae was the dominant family (5 species and 342 individuals). The most abundant echinoderms species was Pearsonothuria graeffei (77 individuals, about 7.81%). Abundances intra-transects and intra-families were insignificant (f = 1.67, p = 0.183, df = 3 and f = 3.24, p = 0.083, df = 9, respectively). The highest values of Shannon-Wiener diversity index (H'), Pielou evenness index (J'), Margalef species richness index (d), and Simpson Dominance index (C) were 2.738, 0.9875, 2.791 and 0.07159, respectively. The distribution patterns of all species in the study transects varied between clumped and uniform, with the exception of Asthenosoma varium of the Echinothuridae family, which had clumped distribution patterns in all transects. The study concluded that Dungonab Bay supports rich and diverse communities of epibenthic echinoderms. 展开更多
关键词 SUDAN Red Sea ECHINODERM diversITY Abundance and distribution
下载PDF
Evaluating the Impacts of Human Activities on Diversity, Abundance, and Distribution of Large Mammals in Nimule National Park, South Sudan
3
作者 Abdallah Gordon Shazali Joseph Mayindo Mayele +1 位作者 Joel Emmanuel Saburi Jubara Nadlin 《Open Journal of Ecology》 2024年第5期483-507,共25页
Globally, human activities have a significant impact on the diversity, abundance, and distribution of large mammals in Protected Areas (PAs). These disturbances increase human pressure on biodiversity and species habi... Globally, human activities have a significant impact on the diversity, abundance, and distribution of large mammals in Protected Areas (PAs). These disturbances increase human pressure on biodiversity and species habitats, highlighting the need for conservation. This study aimed to assess the abundance and distribution of large mammals in different habitat types within Nimule National Park (NNP) and understand the impacts of human activities on them. Data on the abundance and distribution of large mammals and their respective habitat types were collected through line transect surveys. Human activity signs were observed and recorded along the transect lines. To estimate the impacts of human activities on the diversity, abundance, and distribution of large mammal species, as well as to identify any significant differences between them and their habitat types, the study utilized the Kruskal Wallis test, Polynomial multiple regressions, and diversity indices. The findings from the Shannon-Weiner and Simpson indices indicated that large mammal species were more diverse inside the park (H’ = 1.136;D = 0.570) compared to the buffer zone (H’ = 0.413;D = 0.171), with 85% (443 out of 510 samples) recorded within Nimule National Park. The species abundance showed a semi-balanced status (0.58). The diversity results among different habitat types revealed that large mammals were more diverse and highly distributed in both open woodlands (244) and dense woodlands (192), while riverine vegetation had the lowest diversity (8). Statistical tests demonstrated a highly significant difference at a 99% confidence interval (p-value = 0.01) between habitat types and identified species of large mammals. Additionally, the results highlighted the high abundance of Uganda kob (274), baboons (141), and warthog (57) across most habitat types, accounting for at least 75% of their distribution. The most prevalent human activities observed were cattle footprints (27%) and cattle dung (14%). Human footprints and tree cutting combined accounted for 9%, indicating the practice of livestock grazing, poaching, encroachment, and fuelwood collection by local communities. However, these activities did not appear to significantly impact the diversity, abundance, and distribution of large mammals in Nimule National Park. Therefore, it is crucial to foster shared responsibilities and engage relevant stakeholders in the management and conservation of large wildlife species. Regular community awareness programs should be implemented to cultivate a sense of ownership. Moreover, it is recommended that a comprehensive survey be conducted on the population status of all mammal species in Nimule National Park, including its surrounding Buffer Zone. Monitoring the impact of human activities on their behavior and habitats using satellite images should also be carried out at least every five to ten years. 展开更多
关键词 diversity of Large Mammals Abundance and distribution IMPACTS Biodiversity Conservation Human Activities Nimule National Park South Sudan
下载PDF
Fracture propagation law of temporary plugging and diversion fracturing in shale reservoirs under completion experiments of horizontal well with multi-cluster sand jetting perforation
4
作者 ZOU Yushi LI Yanchao +3 位作者 YANG Can ZHANG Shicheng MA Xinfang ZOU Longqing 《Petroleum Exploration and Development》 SCIE 2024年第3期715-726,共12页
This study conducted temporary plugging and diversion fracturing(TPDF)experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion w... This study conducted temporary plugging and diversion fracturing(TPDF)experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion with multi-cluster sand jetting perforation.The effects of temporary plugging agent(TPA)particle size,TPA concentration,single-cluster perforation number and cluster number on plugging pressure,multi-fracture diversion pattern and distribution of TPAs were investigated.A combination of TPAs with small particle sizes within the fracture and large particle sizes within the segment is conducive to increasing the plugging pressure and promoting the diversion of multi-fractures.The addition of fibers can quickly achieve ultra-high pressure,but it may lead to longitudinal fractures extending along the wellbore.The temporary plugging peak pressure increases with an increase in the concentration of the TPA,reaching a peak at a certain concentration,and further increases do not significantly improve the temporary plugging peak pressure.The breaking pressure and temporary plugging peak pressure show a decreasing trend with an increase in single-cluster perforation number.A lower number of single-cluster perforations is beneficial for increasing the breaking pressure and temporary plugging peak pressure,and it has a more significant control on the propagation of multi-cluster fractures.A lower number of clusters is not conducive to increasing the total number and complexity of artificial fractures,while a higher number of clusters makes it difficult to achieve effective plugging.The TPAs within the fracture is mainly concentrated in the complex fracture areas,especially at the intersections of fractures.Meanwhile,the TPAs within the segment are primarily distributed near the perforation cluster apertures which initiated complex fractures. 展开更多
关键词 shale temporary plugging and diversion fracturing multi-cluster sand jetting perforation distribution of temporary plugging agent fracture propagation law
下载PDF
Diversity and geographical distribution of haptophyte Phaeocystis in the Chinese seas based on metabarcoding analysis
5
作者 Qingshang SONG Yue XUE +2 位作者 Yanying ZHANG Jiehui YIN Pingping SHEN 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2023年第6期2197-2207,共11页
Phaeocystis is an important bloom-forming species and over 100 blooms have occurred since 1997 along the Chinese coasts,while only the species P.globosa was described.In this project,a total of 246 phytoplankton sampl... Phaeocystis is an important bloom-forming species and over 100 blooms have occurred since 1997 along the Chinese coasts,while only the species P.globosa was described.In this project,a total of 246 phytoplankton samples collected from the Bohai Sea,the Yellow Sea,and the East China Sea in April 2021 were analyzed to evaluate the species diversity and geographical distribution of the genus Phaeocystis based on metabarcoding 18S r DNA sequence.Four described Phaeocystis species were recognized,including P.globosa,P.pouchetii,P.jahnii,and P.cordata,and each has distinguished geographical distribution characteristics.P.globosa was the most widespread and abundant species,and P.pouchetii was found in the Bohai Sea and the northern Yellow Sea with substantially elevated abundance.P.cordata was also a widespread species,but its abundance was relatively low,while P.jahnii gathered only in the southeastern East China Sea.Water temperature,phosphate as well as ammonium contents were found to be associated with the abundance of P.globosa,P.pouchetii,and P.jahnii significantly.Moreover,two uncharacterized Phaeocystis species were detected in the Chinese seas,indicating the diversity of the genus remains underestimated worldwide. 展开更多
关键词 HAPTOPHYTA PHAEOCYSTIS species diversity distribution Chinese seas amplicon sequence variant
下载PDF
Endemic medicinal plant distribution correlated with stable climate,precipitation,and cultural diversity
6
作者 Gang Feng Ying-Jie Xiong +2 位作者 Hua-Yu Wei Yao Li Ling-Feng Mao 《Plant Diversity》 SCIE CAS CSCD 2023年第4期479-484,共6页
Medicinal plants provide crucial ecosystem services,especially in developing countries such as China,which harbors diverse endemic medicinal plant species with substantial cultural and economic value.Accordingly,under... Medicinal plants provide crucial ecosystem services,especially in developing countries such as China,which harbors diverse endemic medicinal plant species with substantial cultural and economic value.Accordingly,understanding the patterns and drivers of medicinal plant distribution is critical.However,few studies have investigated the patterns and drivers of endemic medicinal plants distribution in China.Here,we linked endemic medicinal plants distribution with possible explanatory variables,i.e.,paleoclimate change,contemporary climate,altitudinal range and ethnic minority human population size at the prefecture city level in China.Our results show that endemic medicinal plants are concentrated in southern China,especially in southwestern China.Notably,both endemic medicinal plant species richness and the ratio of endemic medicinal plant species richness are negatively associated with glacialinterglacial anomaly in temperature,and positively associated with contemporary precipitation and altitudinal range.In addition,we found that endemic medicinal plant species richness is positively associated with ethnic minority population sizes as well as its ratio to the overall population size.These findings suggest that the distribution of endemic medicinal plants is determined by multiple drivers.Furthermore,our findings stress that dramatic future climate changes and massive anthropogenic activities in southern China pose great challenges to the conservation of China's endemic medicinal plants. 展开更多
关键词 Altitudinal range Cultural diversity Endemic medicinal plant Glacial-interglacial climate change PRECIPITATION Spatial distribution
下载PDF
Diversity and Distribution of Wild Musa in Nagaland, India
7
作者 Chitta Ranjan Deb Punatemjen Tiatemsu +1 位作者 Thejavitsu Noah Vupru Asosii Paul 《Open Journal of Forestry》 2023年第3期315-337,共23页
The state of Nagaland is located in a region known to be a micro-centre of Musa evolution. The prevailing agro-climatic conditions are known to support various members of the genus. This study documents 12 species, wh... The state of Nagaland is located in a region known to be a micro-centre of Musa evolution. The prevailing agro-climatic conditions are known to support various members of the genus. This study documents 12 species, which is an ideal representation of the rich diversity of this genus in an area of 16,579 sq. km. The various species were classified using morphological descriptors based on INIBAP, 1996 following the subsequent collection of the live specimen. The various species documented have been found to exist in single populations or in association with other species and their distribution depends on the varying altitudinal profile as well as the agro-climatic and topographical condition of the environment. 展开更多
关键词 DESCRIPTORS Wild Musa diversity Musa distribution Nagaland
下载PDF
Numerical simulation of 80 ℃ temperature field distribution of thick plate multi-pass welding with SYSWELD 被引量:4
8
作者 Han Tao Zhang Hongjie +3 位作者 Wu Qian Bao Liangliang Zhu Xiaoyu Ding Ling 《China Welding》 EI CAS 2018年第1期20-25,共6页
The PPG PITT-CHAR XP flame retardant system has been used by COOEC to preventing the thermal softening of steel in the high temperature,whose degradation temperature is 80 ℃.To prevent damage to PPG PITT-CHAR XP fire... The PPG PITT-CHAR XP flame retardant system has been used by COOEC to preventing the thermal softening of steel in the high temperature,whose degradation temperature is 80 ℃.To prevent damage to PPG PITT-CHAR XP fire retardant paint from excessive heat during welding,it is necessary to get accurately reserved area near the welding joints prior to welding. For the foregoing reasons,the 80 ℃ temperature field distribution of thick plate multi-pass welding was analyzed with SYSWELD.The influence of welding groove form and time interval on welding temperature field was also analyzed. Results showed that the range of 80 ℃ welding temperature field increased with the increasing of weld layers at first and then it inclined to stable value. Interpass time setting was crucial to control the range of 80 ℃ welding temperature field. It was also found that double V groove had better thermal diffusivity than double-bevel groove.And double-bevel groove was better than single V groove. 展开更多
关键词 THICK plate MULTI-PASS WELDING SYSWELD 80℃temperature FIELD distribution
下载PDF
Diversity and distribution of soil micro-fungi along an elevation gradient on the north slope of Changbai Mountain 被引量:2
9
作者 Hong Yang Guozhong Lu +2 位作者 Huiming Jiang Dong-ning Shi Zhiheng Liu 《Journal of Forestry Research》 SCIE CAS CSCD 2017年第4期831-839,共9页
Elevational changes in patterns of diversity are important to understanding of the influence of global changes, yet few studies have addressed the distribution of microorganisms, e.g. soil micro-fungi. We studied the ... Elevational changes in patterns of diversity are important to understanding of the influence of global changes, yet few studies have addressed the distribution of microorganisms, e.g. soil micro-fungi. We studied the diversity of the forest soil micro-fungi in four vegetation belts along an elevation gradient on the north slope of Changbai Mountain in Changbai National Nature Reserve. The four belts were characterized as coniferous-deciduous mixed forest, coniferous forest, Erman's birch forest, and alpine tundra. We estimated the quantity and distribution of the fungal species in each belt and calculated three indices, viz. Shannon-Wiener diversity (H'), Pielou's evenness (J'), and Margalef's abundance (E), to depict fungal species diversity. A total of 932 strains were recorded and identified, representing 53 genera, and 108 species. Among these, Penicillium, Aspergillus, Trichoderma, Mucor, Rhizopus and Fusarium were the dominant genera. With increasing elevation, the quantity of fungi and values of H', E, and J' gradually declined. 展开更多
关键词 Altitudinal gradient distribution diversities Micro-fungi
下载PDF
Species Diversity and Elevational Distribution of Amphibians in the Xianxialing and Wuyishan Mountain Ranges,Southeastern China 被引量:2
10
作者 Zhiqiang CHEN Yun TANG +3 位作者 Yingying WANG Yindie LI Longhui LIN Guohua DING 《Asian Herpetological Research》 SCIE CSCD 2020年第1期44-55,共12页
The species diversity and altitudinal distribution of amphibians along an eleva tional gradient of 200-1600 m in the Xianxialing and Wuyishan Mountain Ranges in Southeastern China were investiga ted through time-const... The species diversity and altitudinal distribution of amphibians along an eleva tional gradient of 200-1600 m in the Xianxialing and Wuyishan Mountain Ranges in Southeastern China were investiga ted through time-constra ined visual surveys along 32 transect lines in 9 survey areas,in which the ha bitat types were also recorded.A total of 27 amphibian species belonging to 19 genera,7 families,and 2 orders were found.The species diversity of the amphibians plateaued at low elevation,and the altitudinal boundary of their distribution was at 800 m.Their species compositions were dissimilar in the two mountain ranges probably beca use the annual average temperature and annual rainfall were different in both areas.The eleva tional Rapoport's rule demonstrated that the species range size of the amphibians expanded as the elevation increased in both mountain ranges.The results of the cross species method supported the rule only when the influence of the low-frequency occurrence proba bility of an investigated species was excluded,whereas those of the Steven's method strongly corroborated the rule rega rdless of the incidental occurrence or absence of the species. 展开更多
关键词 AMPHIBIAN diversity altitudinal distribution Rapoport’s rule CROSS-SPECIES METHOD Steven’s METHOD
下载PDF
Genetic structure associated with diversity and geographic distribution in the USDA rice world collection 被引量:4
11
作者 Hesham A. Agrama WenGui Yan +2 位作者 Melissa Jia Robert Fjellstrom Anna M. McClung 《Natural Science》 2010年第4期247-291,共45页
Cultivated rice (Oryza sativa L.) is structured into five genetic groups, indica, aus, tropical japonica, temperate japonica and aromatic. Genetic characterization of rice germplasm collections will enhance their util... Cultivated rice (Oryza sativa L.) is structured into five genetic groups, indica, aus, tropical japonica, temperate japonica and aromatic. Genetic characterization of rice germplasm collections will enhance their utilization by the global research community for improvement of rice. The USDA world collection of rice germ-plasm that was initiated in 1904 has resulted in over 18,000 accessions from 116 countries, but their ancestry information is not available. A core subset, including 1,763 accessions repre-senting the collection, was genotyped using 72 genome-wide SSR markers, and analyzed for genetic structure, genetic relationship, global distribution and genetic diversity. Ancestry analysis proportioned this collection to 35% indica, 27% temperate japonica, 24% tropical japonica, 10% aus and 4% aromatic. Graphing model-based ancestry coefficients demon-strated that tropical japonica showed up mainly in the American continents and part of the South Pacific and Oceania, and temperate japonica in Europe and the North Pacific far from the equator, which matched the responses to tem-perature. Indica is adapted to the warm areas of Southern Asia, South China, Southeast Asia, South Pacific and Central Africa and around the equator while aus and aromatic are special types of rice that concentrates in Bangladesh and India. Indica and aus were highly diversified while temperate and tropical japonicas had low diversity, indicated by average alleles and pri-vate alleles per locus. Aromatic has the most polymorphic information content. Indica and aromatic were genetically closer to tropical ja-ponica than temperate japonica. This study of global rice has found significant population stratification generally corresponding to major geographic regions of the world. 展开更多
关键词 Genetic Structure RICE ANCESTRY GERMPLASM COLLECTION Molecular diversITY Global distribution
下载PDF
Historical biogeography and evolutionary diversification of Lilium(Liliaceae): New insights from plastome phylogenomics 被引量:1
12
作者 Nian Zhou Ke Miao +4 位作者 Changkun Liu Linbo Jia Jinjin Hu Yongjiang Huang Yunheng Ji 《Plant Diversity》 SCIE CAS CSCD 2024年第2期219-228,共10页
Here, we infer the historical biogeography and evolutionary diversification of the genus Lilium. For this purpose, we used the complete plastomes of 64 currently accepted species in the genus Lilium(14plastomes were n... Here, we infer the historical biogeography and evolutionary diversification of the genus Lilium. For this purpose, we used the complete plastomes of 64 currently accepted species in the genus Lilium(14plastomes were newly sequenced) to recover the phylogenetic backbone of the genus and a timecalibrated phylogenetic framework to estimate biogeographical history scenarios and evolutionary diversification rates of Lilium. Our results suggest that ancient climatic changes and geological tectonic activities jointly shaped the distribution range and drove evolutionary radiation of Lilium, including the Middle Miocene Climate Optimum(MMCO), the late Miocene global cooling, as well as the successive uplift of the Qinghai-Tibet Plateau(QTP) and the strengthening of the monsoon climate in East Asia during the late Miocene and the Pliocene. This case study suggests that the unique geological and climatic events in the Neogene of East Asia, in particular the uplift of QTP and the enhancement of monsoonal climate, may have played an essential role in formation of uneven distribution of plant diversity in the Northern Hemisphere. 展开更多
关键词 Asian monsoon Climatic changes distribution range Evolutionary complexity Radiative diversification Species diversity Qinghai-Tibet plateau(QTP)
下载PDF
Diversity and Distribution of Host Animal Species of Hantavirus and Risk to Human Health in Jiuhua Mountain Area,China 被引量:7
13
作者 HU Xing Qiang LI Shi Guang +2 位作者 LIU Hong WANG Jun HUA Ri Mao 《Biomedical and Environmental Sciences》 SCIE CAS CSCD 2014年第11期849-857,共9页
Objective To investigate the diversity and the distribution of host animal species of hantavirus and the effect on human health in Jiuhua Mountain area,China.Methods The host animal species of hantavirus was surveyed ... Objective To investigate the diversity and the distribution of host animal species of hantavirus and the effect on human health in Jiuhua Mountain area,China.Methods The host animal species of hantavirus was surveyed by using the trap method and the species diversity was evaluated by using the Simpson,Shannon-Weaner,and Pielou indices.Hantavirus antigens or antibodies in lung and blood samples of all the captured host animals were detected by direct or indirect immunofluorescence.Results Nine animal species of hantavirus were distributed in the forest ecosystem of Jiuhua Mountain.Of these,Niviventer confucianus and Apodemus agrarius were predominant,and N.confucianus,Rattus norvegicus,and Mus musculus had relatively large niche breadth index values.The host animals in the eastern and western mountain regions shared similar biodiversity index characteristics,predominant species,and species structures.Hantavirus was detected in 5 host animal species in Jiuhua Mountain area,the carriage rate of hantavirus was 6.03%.The average density of host animals in forest areas of the mountainous area was only 2.20%,and the virus infection rate in the healthy population was 2.33%.Conclusion The circulation of hantavirus was low in the forest areas of Jiuhua Mountain and did not pose a threat to human health. 展开更多
关键词 Hantavirus Host animal diversity and distribution Risk assessment Jiuhua Mountain
下载PDF
Distribution and conservation of near threatened plants in China
14
作者 Qin Liu Tian-Tian Xue +6 位作者 Xiao-Xia Zhang Xu-Dong Yang Fei Qin Wen-Di Zhang Lei Wu Rainer W.Bussmann Sheng-Xiang Yu 《Plant Diversity》 SCIE CAS CSCD 2023年第3期272-283,共12页
Plants classified as Near Threatened(NT) are at high risk of becoming threatened because of anthropogenic interference and climate change.Especially in conservation efforts,such species have however long been overlook... Plants classified as Near Threatened(NT) are at high risk of becoming threatened because of anthropogenic interference and climate change.Especially in conservation efforts,such species have however long been overlooked.Here,we obtained 98,419 precise occurrence points for 2442 NT plants in China,and used species richness,species complementarity,and weighted endemism that consider all,endemic and narrow-ranged species in order to identify the diversity hotspots of NT plants.Then we evaluated the conservation effectiveness of current nature reserves for them.Our results indicate that the diversity hotspots of NT plants were mainly confined to southwestern and southern China,and only 35.87% of hotspots and 71.5% of species were protected by nature reserves.Numerous hotspots in southwestern China(e.g.,Sichuan,Yunnan,Guangxi,and Hainan) were identified as conservation gaps.Given that NT plants include large proportions of endemic and narrow-ranged species,they represent an important value in conservation priority.So,more conservation efforts in the future should be tilted towards NT plants.Additionally,when comparing with the recently updated NT list,there are already 87 species raised to threatened categories,while 328 species were lowered to least concern,56 species were now categorized as data deficient,and 119 species considered as uncertain due to changes of scientific names.It is essential to carry out a continuous assessment of species’ threatened categories to realize targeting conservation. 展开更多
关键词 CONSERVATION distribution patterns diversity hotspots Nature reserves Red list Near threatened species
下载PDF
Influence of porosity distribution on nonlinear free vibration and transient responses of porous functionally graded skew plates 被引量:4
15
作者 Naveen Kumar H S Subhaschandra Kattimani TNguyen-Thoi 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2021年第6期1918-1935,共18页
This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew(PFGS)plates.The effective material properties of... This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew(PFGS)plates.The effective material properties of the PFGS plates are obtained from the modified power-law equations in which gradation varies through the thickness of the PFGS plate.A nonlinear finite element(FE)formulation for the overall PFGS plate is derived by adopting first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinear strain displacement relations.The governing equations of the PFGS plate are derived using the principle of virtual work.The direct iterative method and Newmark’s integration technique are espoused to solve nonlinear mathematical relations.The influences of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the PFGS plate for different skew angles are studied in various parameters.The effects of volume fraction grading index and skew angle on the plate’s nonlinear dynamic responses for various porosity distributions are illustrated in detail. 展开更多
关键词 Porous functionally graded skew plates Porosity distributions Nonlinear transient response Nonlinear frequency ratio Nonlinear frequency parameter
下载PDF
Phytogeographical Distribution and Fruit Diversity of <i>Lagenaria siceraria</i>Species in Nigeria 被引量:1
16
作者 Fortune O. Awala Benjamin C. Ndukwu Ikechukwu O. Agbagwa 《American Journal of Plant Sciences》 2019年第6期958-975,共18页
Phytogeographical distribution and fruit diversity of Lagenaria siceraria (Mol.) Standl species in Nigeria were accessed. Information on the distribution and fruit diversity was sourced from three herbaria, Forestry R... Phytogeographical distribution and fruit diversity of Lagenaria siceraria (Mol.) Standl species in Nigeria were accessed. Information on the distribution and fruit diversity was sourced from three herbaria, Forestry Research Institute of Nigeria Herberia, University of Port Harcourt Herberia and the University of Ibadan Herberia. A field survey across fifteen states in Nigeria namely Kaduna, Kano, Plateau, Oyo, Akwa Ibom, Cross River, Taraba, Bayelsa and Enugu, Ebonyi, Ondo, Ogun, Kwara Anambra and Rivers State. A total of twenty-four fruit shapes were accessed. The diversity of fruit shapes across the geographical regions of Nigeria shows that the Guinea savannah has all the twenty-four different landraces represented, while Tropical rain forest has nineteen, Sudan savannah has seventeen and Freshwater swamp and the Saltwater swamp has eleven different fruit shapes respectively. The fruits of Lagenaria siceraria (Mol) Standl is considered a topocline since it is not affected only by environmental factors but possess a wide distribution pattern across the geographical regions of Nigeria. 展开更多
关键词 FRUIT diversITY Lagenaria siceraria (Mol) Standl Topocline Ecocline and Phytogeographical distribution
下载PDF
Prediction of Potential Distribution of the Genus Cricotopus(Diptera:Chironomidae)Based on MaxEnt Model
17
作者 Zigang XU Yuanyuan YAO +4 位作者 Qing CHEN Panpan XIANG Jingru SHANGGUAN Shiwang LIU Yue FU 《Agricultural Biotechnology》 2023年第6期39-44,47,共7页
The prediction of suitable area is a method for predicting the potential distribution by using the maximum entropy model.This study predicted the potential suitable habitats for the genus Cricotopus of Chironomidae in... The prediction of suitable area is a method for predicting the potential distribution by using the maximum entropy model.This study predicted the potential suitable habitats for the genus Cricotopus of Chironomidae in China.The latitude and longitude information of 98 distribution sites of Cricotopus in China and the biological environmental factors and altitude distribution in China were collected,and suitable habitats for Cricotopus were predicted,obtaining the suitable ranges and areas of Cricotopus in China,which is consistent with the known living conditions of Cricotopus.The study on the diversity of Cricotopus and the prediction of its suitable habitats provide a theoretical basis for Cricotopus in water monitoring and paddy fields,as well as basic data for the study on the genus Cricotopus. 展开更多
关键词 Cricotopus diversITY Prediction of suitable area Geographical distribution
下载PDF
Geographical Distribution and Diversity History of Late Cambrian and Ordovician Gastropods in China
18
作者 LI Wenjie FANG Xiang ZHANG Yuandong 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2019年第S01期119-122,共4页
1 Introduction Gastropods are one of the most diverse groups in the living animals.The rich,long-ranging and extensive occurrences of gastropod fossils make them a unique animal group for evolutionary,ecologic,and bio... 1 Introduction Gastropods are one of the most diverse groups in the living animals.The rich,long-ranging and extensive occurrences of gastropod fossils make them a unique animal group for evolutionary,ecologic,and biogeographic studies(Fryda and Rohr,2004).As a major component of shallow-water benthic fauna. 展开更多
关键词 GASTROPODS ORDOVICIAN distribution diversITY China
下载PDF
NUMERICAL STUDY ON FLOW DISTRIBUTION IN PLATE-FIN HEAT EXCHANGERS
19
作者 张哲 厉彦忠 《Journal of Pharmaceutical Analysis》 SCIE CAS 2003年第2期162-165,共4页
Objective To investigate the flow distribution in plate fin heat exchangers and optimize the design of header configuration for plate fin heat exchangers. Methods A mathematical model of header was proposed. The e... Objective To investigate the flow distribution in plate fin heat exchangers and optimize the design of header configuration for plate fin heat exchangers. Methods A mathematical model of header was proposed. The effects of the header configuration on the flow distribution in plate fin heat exchangers were investigated by CFD. The second header configuration with a two stage distributing structure was brought forward to improve the performance of flow distribution. Results It is found that the flow maldistribution is very serious in the direction of header length for the conventional header used in industry. The numerical predictions indicate that the improved header configurations can effectively improve the performance of flow distribution in plate fin heat exchangers. Conclusion The numerical simulation confirms that CFD should be a suitable tool for predicting the flow distribution. The method has a wide variety of applications in the design of plate fin heat exchangers. 展开更多
关键词 plate fin heat exchanger flow distribution header configuration CFD
下载PDF
Distribution and Diversity of Candida tropicalis Strains in Different Marine Environments
20
作者 YAN Kuiran ZHANG Ying CHI Zhenming 《Journal of Ocean University of China》 SCIE CAS 2010年第2期139-144,共6页
1089 strains of yeasts were obtained from seawater,sea sediments,mud of sea salterns,guts of marine fishes,mangroveplants and marine algae.The results of routine identification and molecular analysis methods show that... 1089 strains of yeasts were obtained from seawater,sea sediments,mud of sea salterns,guts of marine fishes,mangroveplants and marine algae.The results of routine identification and molecular analysis methods show that 44 strains among the marineyeasts obtained in this study belong to Candida tropicalis,which may indicate its wide distribution in different environment,especially in the tropical and subtropical marine environment.The wide distribution of C.tropicalis indicates that it may play an important role in marine environment and the marine environment in turn is a good source for obtaining C.tropicalis. 展开更多
关键词 marine yeasts Candida tropicalis distribution diversITY APPLICATIONS
下载PDF
上一页 1 2 133 下一页 到第
使用帮助 返回顶部