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751.
We examine the intrasecular morphodynamics of the Irkut river within the Tunkinskaya depression and the associated partitions between depressions. An analysis is made of the changes in the channel pattern in plan, and a typization is provided for the channel processes for three time intervals: 1914, 1975 and 2015. We identified eleven morphodynamically uniform reaches of the channel: three, one and seven of them are of the adapted, incised and broad-floodplain types, respectively. The types of morphodynamical development of the river are systematized, and reaches with a different degree of deformation are identified within the most mobile broad-band segment of the river in conditions of free meandering. It is ascertained that the reaches of the braided type and the reach with sharp loop-like bends are the most stable, which is, in either case, due to the consolidation of vegetation by the high floodplain which made it possible to stabilize the movement of the channel in plan. The most strongly altered reaches are determined, where river channel displacements were accompanied by a complete change of the morphodynamical types of bends; the macrobends mainly experienced a regular breakthrough or were complicated by lower-order bends. We identified the reaches with lower-order (local) changes where the development of the bends (for the most part, of the loop-like type) changed into a new evolutionary cycle). We determined the role played by the influence of the territory’s geologo-geomorphological structure, hydrological conditions and natural processes of channel evolution on the dynamics of homogeneous reaches, and on morphological changes within them. The period of the most significant channel deformations, from 1914 to 1976, was determined, which is accounted for by an enhancement in anthropogenic pressure and by the associated increase in suspended load, and the period of decrease in the magnitude of manifestations of channel deformations from 1976 to 2015. 相似文献
752.
A. Yu. Aleksandrova 《Geography and Natural Resources》2016,37(1):18-25
A multifactor tourism typology of countries of the world having a structural-functional character has been developed. It provides insight into the typological features of the global spatial structure of international tourism, reflecting the intensity of international tourism flows, their geography, the importance of the tourism industry for the national economy as well as the general attributes of territorial organization of international tourism, and the dynamics of its development. Five main types of touristic types of countries have been identified. The following indicators were used for characterization of the countries and their comparison: the size of the territory, and the population size; the general level of socioeconomic development; the level and character of development of international tourism; the characteristic properties of touristic demand; the orientedness of tourism flows; characteristics of touristic offer; the degree of influence of international tourism on the national economy; characteristics of the state policy in the sphere of tourism, and touristic specialization. The first type includes the economically highly developed countries with mature national systems of international tourism forming the center of the world’s touristic space. The second type is represented by countries belonging to the semi-periphery of the world’s touristic space with an intensely forming state-supported polyfunctional system of international tourism. The third type includes moderately developed countries of the semi-periphery of the world’s touristic space with a polyfunctional system of international tourism in the stage of transformation and formation of a civilized travel market. The fourth type comprises small island states of the Caribbean Basin which belong to the semi-periphery and, in part, to the “advanced” periphery of the world’s touristic space. The fifth type combines developing countries belonging to the periphery of the world’s touristic space, with a weakly developed market of international tourism. 相似文献
753.
754.
As an effective livelihood approach to alleviate poverty without rural population migration, ethnic tourism has become the primary choice of economic development in ethnic areas worldwide in addition to traditional livelihood approaches. This article applies the theories of livelihood to study the community evolution driven by tourism livelihood and examine three mountainous tourism communities in different stages of tourist area life cycle. Drawing on the methods of GIS spatial analysis, semi-structured interviews and questionnaires, this article proposes a sustainable livelihood framework for ethnic tourism to explore the evolution of ethnic tourism communities by identifying changes in livelihood assets (natural, financial, social, cultural and human capitals) in the process of tourism development. The results show that the development of ethnic tourism has led to changes in the increase of building land, and the diversification of land use functions with a trend of shifting from meeting local villagers' living needs to satisfying tourists, income composition and uneven distribution of tourism income spatially. Ethnic tourism also led to the deterioration of traditional social management structure, collapse of neighboring relationship, the over- commercialization and staged authenticity of ethnic culture, as well as the gradual vanish of agricultural knowledge with a trend of increasing modern business knowledge and higher education. In addition, these changes, involving livelihood assets from natural, economic, human, social and cultural aspects are interrelated and interactive, which form new evolution characters of ethnic community. This study reveals the conflicts over livelihood approaches which have formed new vulnerabilities to impact on sustainable evolution of ethnic communities. This research provides implications for achieving the sustainable development of ethnic communities with the driving force of tourism livelihood. 相似文献
755.
中国城市流动人口户籍迁移意愿的空间格局及影响因素——基于2012年全国流动人口动态监测调查数据 总被引:10,自引:0,他引:10
基于2012年全国流动人口动态监测调查数据和相关统计年鉴数据,对中国地级以上城市流动人口的户籍迁移意愿、空间格局及影响因素进行了系统分析。研究发现,中国城市流动人口户籍迁移意愿的整体水平并不高;等级高、规模大的城市流动人口的户籍迁移意愿高,而等级低、规模小的城市流动人口的户籍迁移意愿低;沿海城市群流动人口的户籍迁移意愿高,其他城市流动人口的户籍迁移意愿低,但内陆部分省会城市和交通区位与资源禀赋较好的中小城市也已经形成了一批流动人口的户籍迁移意愿高值区。中国城市流动人口户籍迁移意愿的空间分布特征受到流入城市和流动人口自身双重力量的影响,流入城市因素的正向影响作用大于流动人口自身因素。其中,流入城市的社会、经济发展水平和流动人口在流入城市的社会融合程度是核心要素,对城市流动人口户籍迁移意愿的提升具有正向的促进作用,而流动人口过于集中在次级劳动力市场的就业特征和较高的家庭财富与收入对户籍迁移意愿的提升却具有显著的抑制作用。最后,提出了相关政策启示。 相似文献
756.
Scapharca broughtonii is a commercially important and over-exploited species. In order to investigate its genetic diversity and population structure, 43 novel polymorphic microsatellites were isolated and characterized. The number of alleles per locus ranged from 3 to 22 with an average of 6.93, and the observed and expected heterozygosities varied between 0.233 and 1.000, and 0.250 and 0.953, with an average of 0.614 and 0.707, respectively. Three highly informative multiplex PCRs were developed from nine of those microsatellites for S. broughtonii. We evaluated and validated these multiplex PCRs in 8 full-sib families. The average polymorphism information content (PIC) was 0.539. The frequency of null alleles was estimated as 3.13% of all the alleles segregation based on a within-family analysis of Mendelian segregation patterns. Parentage analysis of real offspring demonstrated that 100% of all offspring were unambiguously allocated to a pair of parents based on 3 multiplex sets. Those 43 microsatellite loci with high variability will be helpful for the analysis of population genetics and conservation of wild stock of S. broughtonii. The 3 sets of multiplex PCRs could be an important tool of pedigree reconstruction, population genetic analysis and brood stock management. 相似文献
757.
Sulfate-reducing bacteria (SRB), which obtain energy from dissimilatory sulfate reduction, play a vital role in the carbon and sulfur cycles. The dissimilatory sulfite reductase (Dsr), catalyzing the last step in the sulfate reduction pathway, has been found in all known SRB that have been tested so far. In this study, the diversity of SRB was investigated in the surface sediments from the adjacent area of Changjiang Estuary by PCR amplification, cloning and sequencing of the dissimilatory sulfite reductase beta subunit gene (dsrB). Based on dsrB clone libraries constructed in this study, diversified SRB were found, represented by 173 unique OTUs. Certain cloned sequences were associated with Desulfobacteraceae, Desulfobulbaceae, and a large fraction (60%) of novel sequences that have deeply branched groups in the dsrB tree, indicating that novel SRB inhabit the surface sediments. In addition, correlations of the SRB assemblages with environmental factors were analyzed by the linear model-based redundancy analysis (RDA). The result revealed that temperature, salinity and the content of TOC were most closely correlated with the SRB communities. More information on SRB community was obtained by applying the utility of UniFrac to published dsrB gene sequences from this study and other 9 different kinds of marine environments. The results demonstrated that there were highly similar SRB genotypes in the marine and estuarine sediments, and that geographic positions and environmental factors influenced the SRB community distribution. 相似文献
758.
Guangjun Wang Ermeng Yu Zhifei Li Deguang Yu Haiying Wang Wangbao Gong 《中国海洋大学学报(英文版)》2016,15(3):495-501
The present study was conducted to evaluate the feasibility of replacing fish meal (FM) with bioactive peptides (BPs) in diet of white shrimp (Litopenaeus vannamei). The changes in growth performance, body composition, non-specific immunity, and water quality were examined after the shrimp were fed four diets, in which 0% (control), 33.3%, 66.7% and 100% of FM was replaced by BPs, respectively. The groups were designated as Con, 1/3BPs, 2/3BPs, and 3/3BPs. A total of 720 shrimp with an initial body weight of 1.46 ± 0.78 g were fed the experimental diets for 56 days. The results revealed that: 1) the weight gain rate (WGR) in 1/3BPs, 2/3BPs, and 3/3BPs was significantly higher than that in Con (P < 0.05), while no significant difference was found on survival rate and feed conversion ratio (FCR); 2) the whole-body crude protein (CP) and crude lipids (CL) were significantly different among groups, while there was no significant difference between crude ash and phosphorus contents; 3) the levels of acid phosphatase (ACP), lysozyme (LZM), superoxide dismutase (SOD), phenol oxidase (PO) and bactericidal activity increased significantly with the inclusion of BPs; 4) in terms of water quality, no significant difference was found in pH and dissolved oxygen among diets during the whole experimental period. Moreover, even though nitrite and ammonium levels tended to increase with time, there was no significant difference among groups. The results indicated that BPs is an applicable alternative of protein source, which can substitute FM in the diets of L. vannamei; it is able to effectively promote growth performance and improve immunity. Moreover, BPs in the diets had no negative impact on water quality. 相似文献
759.
In order to solve the problem of depth classification of the underwater target in a very low frequency acoustic field, the active component of cross spectra of particle pressure and horizontal velocity (ACCSPPHV) is adopted to distinguish the surface vessel and the underwater target. According to the effective depth of a Pekeris waveguide, the placing depth forecasting equations of passive vertical double vector hydrophones are proposed. Numerical examples show that when the sum of depths of two hydrophones is the effective depth, the sign distribution of ACCSPPHV has nothing to do with horizontal distance; in addition, the sum of the first critical surface and the second critical surface is equal to the effective depth. By setting the first critical surface less than the difference between the effective water depth and the actual water depth, that is, the second critical surface is greater than the actual depth, the three positive and negative regions of the whole ocean volume are equivalent to two positive and negative regions and therefore the depth classification of the underwater target is obtained. Besides, when the 20 m water depth is taken as the first critical surface in the simulation of underwater targets (40 Hz, 50 Hz, and 60 Hz respectively), the effectiveness of the algorithm and the correctness of relevant conclusions are verified, and the analysis of the corresponding forecasting performance is conducted. 相似文献
760.
A hydro-dynamic model is established on basis of MIKE21 FM to simulate the hydro-dynamic characteristics of Xinghua Bay and investigate the influence of reclamation project on the tidal elevation and tidal currents. Tidal elevation data was obtained at the six tide gauge stations around the Xinghua Bay, and another six current stations were established to observe the tidal current velocity and direction. Validation shows that the model-simulated tidal elevation and tidal currents agree well with observations made at different stations. Predictions are made according to the reclamation project proposed in the regional marine planning of Hanjiang Industrial Park around the port in Putian City. The variations of hydro-dynamic factors, such as tide, current velocity and direction and tidal influx are obtained, and the adverse effect of reclamation on marine environment is discussed. It is shown that the tidal level inside the Xinghua Bay during high tide decreases after the reclamation project is completed. The tidal currents during flooding tide generally decrease in the southeast of the reclamation region, with the maximum decreasing amplitude reaching 0.44 m s-1. On the other hand, the tidal currents during flooding tide increase around the southeast and southwest corners of the reclamation region. The tidal currents during ebb tide increase around the southeast and southwest corners of the reclamation region, with the maximum increasing amplitude attaining 0.18 m s-1. The results in this paper can give some guidance for the marine environment management and the effective utilization of land in Putian. 相似文献