oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Railway Network Organization and Spatial Service System Optimization in China
中国铁路客运网络组织与空间服务系统优化

WANG Jiao'e,JIN Fengjun,
王姣娥
,金凤君

地理学报 , 2005,
Abstract: This paper studies the relationship of network organization and spatia l service system optimization based on analyzing the change of intercity passeng er transport network behind railway's upgrading. The authors choose some indexes , including travel time and the coefficient of temporal location, to evaluate th e benefits of 63 cities, accordingly to the reflection of the optimization and c hange of railway network structure. At the same time, the paper especially studi es eight major transport harbors, including Beijing, Shanghai, Guangzhou, Zhengz hou, Wuhan, Shenyang, Chengdu and Lanzhou. Based on the analysis, we found that: (1) Intercity passenger transport network shows remarkable "time-convergence", an indication of the great optimization of the spatial service system. (2) The i nfluences of optimization's spatial distributions are not equilibrium, the chang e of network structure is not remarkable, but it has the trend of equilibrium. ( 3) Railway's upgrading accelerates the interaction of cities, but the benefits o f eight transport hubs are not the same, either; "500 km half a day of activity circle" has already taken shape, "1000 km a day of activity circle" and metropol itan transport circles such as Beijing and Shanghai are being developed graduall y. (4) After the infrastructure network reaches the "universal" stage, the upgra ding of network organization becomes more and more important to optimize the spa tial service system, accelerate the economic interaction. (5) With the expansion of major hub cities' hinterlands and spatial service scopes, sequentially it wi ll bring strong guidance to relocate economic action.
Access and Equity in Basic Education  [cached]
Saqib Shahzad,Riasat Ali,Dr. Hukamdad,Safdar Rehman Ghazi
Asian Social Science , 2010, DOI: 10.5539/ass.v6n8p138
Abstract: Education is the key to development in any society. It is also true to say that the condition of the educational institution in any given society reflects the standard of living and the attitudes towards life of that society. The major purpose of this study was to investigate the access and equity in basic education in Northern. The main objectives of the study were: To assess the extent of availability of primary level schools in West Frontier Province. To compare the reasons of repetition and dropout rates among children at primary level. To understand the views of teachers and parents regarding access and equity in basic education. To recommend some measures for the improvement of basic education in West Frontier Province. Two questionnaires, one for teacher and for parents were administered to collect data. The collected data were tabulated, analyzed and interpreted in the light of objectives of the studies. In the light of conclusions it is recommended that more primary schools should be established for reducing distance from home to school for small children particularly in rural area. Moreover, maximum physical facilities may be provided. Measures should be taken to reduce gender disparity in West Frontier Province. Syllabus may be revised and developed according to the mental level and requirements of the students. Education may be made cheap/free and trained/qualified teachers may be appointed wherever needed.
Spatial Spectrum Access Game  [PDF]
Xu Chen,Jianwei Huang
Computer Science , 2014,
Abstract: A key feature of wireless communications is the spatial reuse. However, the spatial aspect is not yet well understood for the purpose of designing efficient spectrum sharing mechanisms. In this paper, we propose a framework of spatial spectrum access games on directed interference graphs, which can model quite general interference relationship with spatial reuse in wireless networks. We show that a pure Nash equilibrium exists for the two classes of games: (1) any spatial spectrum access games on directed acyclic graphs, and (2) any games satisfying the congestion property on directed trees and directed forests. Under mild technical conditions, the spatial spectrum access games with random backoff and Aloha channel contention mechanisms on undirected graphs also have a pure Nash equilibrium. We also quantify the price of anarchy of the spatial spectrum access game. We then propose a distributed learning algorithm, which only utilizes users' local observations to adaptively adjust the spectrum access strategies. We show that the distributed learning algorithm can converge to an approximate mixed-strategy Nash equilibrium for any spatial spectrum access games. Numerical results demonstrate that the distributed learning algorithm achieves up to superior performance improvement over a random access algorithm.
Spatial disposition of social facilities in the primary school organization  [PDF]
Tani? Milan,Kondi? Slavi?a,Stankovi? Danica
Facta Universitatis Series : Architecture and Civil Engineering , 2011, DOI: 10.2298/fuace1102325t
Abstract: As a consequence of expanding functions of primary schools, the manifestation of social facilities represent an indispensable part of the spatial framework of contemporary pedagogical process with a specially pronounced social component. Irrespective of the size of the school, high level of usability and connectedness of all areas which are often consequentially multifunctional in character, represents one of the basic ways for overcoming of rigid spatial-functional volumes characteristic for architectonic design of traditional schools. In the paper, an analysis of three possible dispositions of social functions was done - of central, linear and dislocated. Conditioned by specific influential factors, for each of the spatial dispositions, functional characteristics have been systematized. On their basis, it was concluded that in optimal conditions of architectonic organization of primary school, application of central disposition can to the best measure contribute to achieving the spatial-functional quality of social functions.
mqr-tree: A 2-dimensional Spatial Access Method  [PDF]
Marc Moreau,Wendy Osborn
Computer Science , 2012,
Abstract: In this paper, we propose the mqr-tree, a two-dimensional spatial access method that organizes spatial objects in a two-dimensional node and based on their spatial relationships. Previously proposed spatial access methods that attempt to maintain spatial relationships between objects in their structures are limited in their incorporation of existing one-dimensional spatial access methods, or have lower space utilization in its nodes, and higher tree height, overcoverage and overlap than is necessary. The mqr-tree utilizes a node organization, set of spatial relationship rules and insertion strategy in order to gain significant improvements in overlap and overcoverage. In addition, other desirable properties are identified as a result of the chosen node organization and insertion strategies. In particular, zero overlap is achieved when the mqr-tree is used to index point data. A comparison of the mqr-tree insertion strategy versus the R-tree shows significant improvements in overlap and overcoverage, with comparable space utilization. In addition, a comparison of region searching shows that the mqr-tree achieves a lower number of disk accesses in many cases
Spatial organization of proteomes: A low-rank approximation  [PDF]
Federico Felizzi,Jerome Galtier,Georgios Fengos,Dagmar Iber
Quantitative Biology , 2012,
Abstract: We investigate the problem of signal transduction via a descriptive analysis of the spatial organization of the complement of proteins exerting a certain function within a cellular compartment. We propose a scheme to assign a numerical value to individual proteins in a protein interaction network by means of a simple optimization algorithm. We test our procedure against datasets focusing on the proteomes in the neurite and soma compartments.
Coordinated Optimization of Visual Cortical Maps (I) Symmetry-based Analysis  [PDF]
Lars Reichl ,Dominik Heide,Siegrid L?wel,Justin C. Crowley,Matthias Kaschube,Fred Wolf
PLOS Computational Biology , 2012, DOI: 10.1371/journal.pcbi.1002466
Abstract: In the primary visual cortex of primates and carnivores, functional architecture can be characterized by maps of various stimulus features such as orientation preference (OP), ocular dominance (OD), and spatial frequency. It is a long-standing question in theoretical neuroscience whether the observed maps should be interpreted as optima of a specific energy functional that summarizes the design principles of cortical functional architecture. A rigorous evaluation of this optimization hypothesis is particularly demanded by recent evidence that the functional architecture of orientation columns precisely follows species invariant quantitative laws. Because it would be desirable to infer the form of such an optimization principle from the biological data, the optimization approach to explain cortical functional architecture raises the following questions: i) What are the genuine ground states of candidate energy functionals and how can they be calculated with precision and rigor? ii) How do differences in candidate optimization principles impact on the predicted map structure and conversely what can be learned about a hypothetical underlying optimization principle from observations on map structure? iii) Is there a way to analyze the coordinated organization of cortical maps predicted by optimization principles in general? To answer these questions we developed a general dynamical systems approach to the combined optimization of visual cortical maps of OP and another scalar feature such as OD or spatial frequency preference. From basic symmetry assumptions we obtain a comprehensive phenomenological classification of possible inter-map coupling energies and examine representative examples. We show that each individual coupling energy leads to a different class of OP solutions with different correlations among the maps such that inferences about the optimization principle from map layout appear viable. We systematically assess whether quantitative laws resembling experimental observations can result from the coordinated optimization of orientation columns with other feature maps.
Spatial Organization and Correlations of Cell Nuclei in Brain Tumors  [PDF]
Yang Jiao,Hal Berman,Tim-Rasmus Kiehl,Salvatore Torquato
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0027323
Abstract: Accepting the hypothesis that cancers are self-organizing, opportunistic systems, it is crucial to understand the collective behavior of cancer cells in their tumorous heterogeneous environment. In the present paper, we ask the following basic question: Is this self-organization of tumor evolution reflected in the manner in which malignant cells are spatially distributed in their heterogeneous environment? We employ a variety of nontrivial statistical microstructural descriptors that arise in the theory of heterogeneous media to characterize the spatial distributions of the nuclei of both benign brain white matter cells and brain glioma cells as obtained from histological images. These descriptors, which include the pair correlation function, structure factor and various nearest neighbor functions, quantify how pairs of cell nuclei are correlated in space in various ways. We map the centroids of the cell nuclei into point distributions to show that while commonly used local spatial statistics (e.g., cell areas and number of neighboring cells) cannot clearly distinguish spatial correlations in distributions of normal and abnormal cell nuclei, their salient structural features are captured very well by the aforementioned microstructural descriptors. We show that the tumorous cells pack more densely than normal cells and exhibit stronger effective repulsions between any pair of cells. Moreover, we demonstrate that brain gliomas are organized in a collective way rather than randomly on intermediate and large length scales. The existence of nontrivial spatial correlations between the abnormal cells strongly supports the view that cancer is not an unorganized collection of malignant cells but rather a complex emergent integrated system.
The yin and yang of chromatin spatial organization
Nathan F Cope, Peter Fraser, Christopher H Eskiw
Genome Biology , 2010, DOI: 10.1186/gb-2010-11-3-204
Abstract: Long-range chromatin interactions can occur over many megabases, either between regions of the same chromosome (cis) or between different chromosomes (trans). Many chromatin clustering events involve preferential interactions between genomic loci and are cell type specific, indicating a functional role of genome organization in regulating gene expression. Many mechanisms are involved in establishing global organization, including transcription by specific sets of transcription factors or gene repression among similar epigenetically marked domains. Here, we discuss several examples of specific spatial organization patterns from transcriptionally active and silent chromatin and the potential mechanisms involved in their establishment.A growing number of specific long-range chromatin interactions have been identified, indicating that the three-dimensional organization of chromatin within the nucleus is not random. These interactions have been found using tools such as RNA and DNA fluorescence in situ hybridization (FISH) and the chromatin proximity-ligation assay chromosome conformation capture (3C) and its derivatives [1]. In 3C, genomic regions in spatial proximity are cross-linked and digested with a restriction enzyme while in the nucleus. After nuclear lysis, the cross-linked chromatin complexes are diluted and ligated such that ends of restriction fragments in the same cross-linked complex form novel ligation junctions that can be detected by various methods. Numerous studies using these tools have shown that the three-dimensional organization of chromatin within the nucleus is not random. One of the best known and studied long-range interactions occurs between the erythroid-specific β-globin gene and its long-range enhancer, the distal locus control region (LCR). The mammalian β-globin LCR consists of five DNase I hypersensitive sites (HS1-HS5) distributed over 15 kb, located approximately 50 kb upstream of the β-globin gene. The LCR regulates β-globin gene tran
Spatial Learning: Conditions and Basic Effects  [cached]
Victoria D. Chamizo
Psicológica , 2002,
Abstract: A growing body of evidence suggests that the spatial and the temporal domains seem to share the same or similar conditions, basic effects, and mechanisms. The blocking, unblocking and overshadowing experiments (and also those of latent inhibition and perceptual learning reviewed by Prados and Redhead in this issue) show that to exclude associative learning as a basic mechanism responsible for spatial learning is quite inappropriate. All these results, especially those obtained with strictly spatial tasks, seem inconsistent with O Keefe and Nadel s account of true spatial learning or locale learning. Their theory claims that this kind of learning is fundamentally different and develops with total independence from other ways of learning (like classical and instrumental conditioning -taxon learning). In fact, the results reviewed can be explained appealing on to a sophisticated guidance system, like for example the one proposed by Leonard and McNaughton (1990; see also McNaughton and cols, 1996). Such a system would allow that an animal generates new space information: given the distance and address from of A to B and from A to C, being able to infer the distance and the address from B to C, even when C is invisible from B (see Chapuis and Varlet, 1987 -the contribution by McLaren in this issue constitutes a good example of a sophisticated guidance system).
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.