Spatial Aggregation in Gravity Models: 4. Generalisations and Large-Scale Applications

1982 ◽  
Vol 14 (6) ◽  
pp. 795-822 ◽  
Author(s):  
M Batty ◽  
P K Sikdar
Keyword(s):  
Large Scale ◽  
Spatial Information ◽  
Spatial Interaction ◽  
Model Performance ◽  
Spatial Aggregation ◽  
Gravity Models ◽  
Future Research ◽  
Data Set ◽  
Four Levels ◽  
Parameter Values

This paper is concerned with applying and extending a methodology for analysing spatial aggregation in gravity models developed in three earlier papers to a larger scale and hence more realistic example of spatial interaction than has been treated so far. Problems of model performance and the analysis of spatial aggregation effects identified in earlier papers are first described, and accordingly the spatial information (entropy) function used previously is then generalised to enable a wider set of models to be applied. Seven models are generated by means of spatial and generalised entropy functions subject to a standard set of model constraints, and the properties of the models in terms of their canonical forms are presented. The models are then applied to four levels of aggregation (234, 121, 58, and 22 zones) of the spatial interaction pattern in Edmonton, Alberta. As in previous papers, information in the data set at the four levels of aggregation is first measured and interpreted, the models are then fitted to these four levels, and relationships between information and parameter values sought. The approximation theory developed earlier is then used to predict parameter values of such models directly from observed spatial information. The results are only fair, better than those of part 3, but worse than those of part 2; although in terms of predicted parameter shift between levels of aggregation, the shifts associated with the doubly constrained model are accurately predicted. The various themes in these papers are then drawn together, conclusions with respect to the value of the insights gained are made, and speculations as to the most fruitful lines for future research outlined.

Spatial Aggregation in Gravity Models: 3. Two-Dimensional Trip Distribution and Location Models

1982 ◽  
Vol 14 (5) ◽  
pp. 629-658 ◽  
Author(s):  
M Batty ◽  
P K Sikdar
Keyword(s):  
Spatial Interaction ◽  
Model Performance ◽  
Spatial Aggregation ◽  
Gravity Models ◽  
Canonical Forms ◽  
Two Dimensional ◽  
Variable Model ◽  
Interaction Models ◽  
Spatial Interaction Models ◽  
Spatial Entropy

This is the third of four papers and in it the methodology for analysing spatial aggregation in gravity models outlined in the first paper is further elaborated. In the second paper, the methodology was applied to one-dimensional spatial interaction models of the population density type, with some success; and here it is proposed to apply the methodology to two-dimensional spatial interaction models using the same data base, the Reading (UK) region. Accordingly, the methodology is first stated for linking information in data measured by spatial entropy to the parameters of models generated from spatial entropy. The family of four spatial interaction models due to Cordey-Hayes and Wilson is then derived, the canonical forms of their associated spatial entropy functions presented, and the analytic properties of such models explored. These four models are then fitted to spatial aggregations of the Reading region, and various empirical relationships between their entropies and parameters described. The results are not as regular as those of the models in the second paper because of more variable model performance, but nevertheless a means of approximating scale parameters from data based on the work of Kirby is outlined. This enables estimates of the dispersion parameters to be made through the canonical forms. Although the results are poor because of model performance, the methodology outlined here serves as a basis for the more fully fledged application to be discussed in the final paper.

Optimal Zoning Systems for Spatial Interaction Models

1977 ◽  
Vol 9 (2) ◽  
pp. 169-184 ◽  
Author(s):  
S Openshaw
Keyword(s):  
Spatial Model ◽  
Model Building ◽  
Spatial Interaction ◽  
Empirical Studies ◽  
Model Performance ◽  
Interaction Models ◽  
Spatial Interaction Models ◽  
Parameter Values ◽  
Zoning Systems

The design of zoning systems for spatial interaction models is a major problem which affects both the interpretation and acceptability of these models. This paper demonstrates that zoning-system effects on parameter values and model performance are nontrivial, and that their magnitude is far larger than was previously thought likely. An approach which is most appropriate in an applied context, where there is also the problem of poor model performance, is to identify a zoning system which will approximately optimise model performance. The paper gives details of how this may be achieved. This method is demonstrated by a series of empirical studies. Finally, there is a brief discussion of the general implications for spatial model building.

Electroconvulsive therapy versus transcranial magnetic stimulation for major depression: a review with recommendations for future research

2008 ◽  
Vol 20 (6) ◽  
pp. 291-294 ◽  
Author(s):  
Keith G. Rasmussen
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Major Depression ◽  
Electroconvulsive Therapy ◽  
Magnetic Stimulation ◽  
Large Scale ◽  
The Elderly ◽  
Future Research ◽  
Sample Sizes ◽  
Data Set ◽  
Differential Outcomes

Objective:To review the literature comparing electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS) for major depression.Methods:Data from the six randomised, prospective studies were agglutinated into one data set. Special attention was given to the methods of both TMS and ECT as well as data pertaining to differential outcomes in subgroups such as psychotic depressives and the elderly.Results:There is a highly significant advantage for ECT in the prospective, randomised trials. The two non-randomised, retrospective comparative trials found the treatments to be equal in one study and superior for ECT in another. However, sample sizes are small in these studies, and both TMS and ECT may have been used suboptimally. Furthermore, the possibilities of differential efficacy of ECT or TMS for psychotic depressives or as a function of age have yet to be fully explored.Conclusions:The data to date do not support the contention that TMS is equivalent in efficacy to ECT. It is recommended that a large-scale trial be undertaken using aggressive forms of both TMS and ECT with sample sizes sufficiently large to detect effects of moderating variables such as age and psychosis status.

Mother nature’s son?

2016 ◽  
Vol 8 (2) ◽  
pp. 137-172 ◽  
Author(s):  
Diana M. Hechavarría
Keyword(s):  
Cultural Values ◽  
Large Scale ◽  
Covariance Structure ◽  
Gender Socialization ◽  
Entrepreneurial Activity ◽  
Future Research ◽  
Female Entrepreneurs ◽  
Data Set ◽  
Content Type ◽  
Country Level

Purpose Drawing on the multiplicity of context approach, this study investigates whether female entrepreneurs are more likely than male entrepreneurs to create environmentally oriented organizations. This study aims to examine how context, measured by gender socialization stereotypes and post-materialism, differentially affects the kinds of organizations entrepreneurs choose to create. Design/methodology/approach To test the hypotheses, this study utilizes Global Entrepreneurship Monitor data from 2009 (n = 17,364) for nascent entrepreneurs, baby businesses owners and established business owners in 47 counties. This study also utilizes the World Values Surveys to measure gender ideologies and post-materialist cultural values at the country level. To test the hypotheses, a logistic multi-level model is estimated to identify the drivers of environmental venturing. Data are nested by countries, and this allows random intercepts by countries with a variance components covariance structure. Findings Findings indicate that female entrepreneurs are more likely to engage in ecological venturing. Societies with high levels of post-materialist national values are significantly more likely to affect female entrepreneurs to engage in environmental ventures when compared to male entrepreneurs. Moreover, traditional gender socialization stereotypes decrease the probability of engaging in environmental entrepreneurship. Likewise, female entrepreneurs in societies with strong stereotypes regarding gender socialization will more likely engage in environmental entrepreneurship than male entrepreneurs. Research limitations/implications The present study uses a gender analysis approach to investigate empirical differences in environmental entrepreneurial activity based on biological sex. However, this research assumes that gender is the driver behind variations in ecopreneurship emphasis between the engagement of males and females in venturing activity. The findings suggest that female entrepreneurs pursuing ecological ventures are more strongly influenced by contextual factors, when compared to male entrepreneurs. Future research can build upon these findings by applying a more nuanced view of gender via constructivist approaches. Originality/value This study is one of the few to investigate ecologically oriented ventures with large-scale empirical data by utilizing a 47-country data set. As a result, it begins to open the black box of environmental entrepreneurship by investigating the role of gender, seeking to understand if men and women entrepreneurs equally engage in environmental venturing. And it responds to calls that request more research at the intersection of gender and context in terms of environmental entrepreneurship.

Spatial Aggregation in Gravity Models: 2. One-Dimensional Population Density Models

1982 ◽  
Vol 14 (4) ◽  
pp. 525-553 ◽  
Author(s):  
M Batty ◽  
P K Sikdarfl
Keyword(s):  
Population Density ◽  
Spatial Information ◽  
Interaction Model ◽  
Theoretical Models ◽  
Spatial Aggregation ◽  
Gravity Models ◽  
Model Parameters ◽  
One Dimensional ◽  
Dimensional Interaction ◽  
Population Density Model

This paper, the second of four, is concerned with applying a methodology for analysing the spatial aggregation problem in gravity models outlined in the first paper. The methodology is based on a consistent framework for linking measures of pattern in interaction data to the derivation and estimation of related interaction models using spatial information theory. In this quest, a link is forged between information in data and the parameters of an associated model, and in part 1 it was suggested that if this link could be formalised then a means would be available for predicting changes in model parameters from different aggregations of the data, prior to the actual estimation of the models themselves. This relationship can be formalised for the case of the continuous one-dimensional interaction model such as the population density model, and this paper is concerned with demonstrating such an application to aggregations of zones in the Reading region. The framework is first described and two continuous models are presented. Then, the discrete model is estimated by means both of regression and of entropy techniques applied to various aggregations of the region, and the resulting parameters are related to the predicted and observed informations. Finally, the parameters approximated from observed information by use of the theoretical models are compared with the estimated parameters, and the approximation is deemed good, thus providing some confidence in the general concepts developed to handle these types of problem.

scholarly journals Multilevel feature fusion dilated convolutional network for semantic segmentation

2021 ◽  
Vol 18 (2) ◽  
pp. 172988142110076
Author(s):  
Tao Ku ◽  
Qirui Yang ◽  
Hao Zhang
Keyword(s):  
Large Scale ◽  
Semantic Information ◽  
Spatial Information ◽  
Feature Fusion ◽  
Scene Perception ◽  
Semantic Segmentation ◽  
Field Size ◽  
Data Set ◽  
Dilated Convolution ◽  
High Level

Recently, convolutional neural network (CNN) has led to significant improvement in the field of computer vision, especially the improvement of the accuracy and speed of semantic segmentation tasks, which greatly improved robot scene perception. In this article, we propose a multilevel feature fusion dilated convolution network (Refine-DeepLab). By improving the space pyramid pooling structure, we propose a multiscale hybrid dilated convolution module, which captures the rich context information and effectively alleviates the contradiction between the receptive field size and the dilated convolution operation. At the same time, the high-level semantic information and low-level semantic information obtained through multi-level and multi-scale feature extraction can effectively improve the capture of global information and improve the performance of large-scale target segmentation. The encoder–decoder gradually recovers spatial information while capturing high-level semantic information, resulting in sharper object boundaries. Extensive experiments verify the effectiveness of our proposed Refine-DeepLab model, evaluate our approaches thoroughly on the PASCAL VOC 2012 data set without MS COCO data set pretraining, and achieve a state-of-art result of 81.73% mean interaction-over-union in the validate set.

scholarly journals Visualizing Sustainability Research in Business and Management (1990–2019) and Emerging Topics: A Large-Scale Bibliometric Analysis

2019 ◽  
Vol 11 (20) ◽  
pp. 5596 ◽  
Author(s):  
Qiong Jia ◽  
Liyuan Wei ◽  
Xiaotong Li
Keyword(s):  
Economic Growth ◽  
Large Scale ◽  
Future Research ◽  
Data Set ◽  
Holistic View ◽  
Sustainability Research ◽  
Depth Analysis ◽  
Development Goals ◽  
Clear Shift ◽  
Business And Management

While researchers from many disciplines are increasingly interested in studying issues related to sustainability, few studies have presented a holistic view of sustainability from the perspectives of business and management. This bibliometric study quantitatively analyzed a big data set of 30 years of sustainability research (1990–2019), consisting of 37,322 publications and 1,199,398 cited references, visualizing major topics, dynamic evolution, and emerging development. The decade-by-decade in-depth analysis shows a clear shift from a nearly exclusive focus on economic growth and consumption to all three pillars of sustainability, i.e., economic growth, social development, and environmental protection. Highlighting the differences between United Nations’ Sustainable Development Goals and the popular research topics from academia, our analysis uncovers research gaps and suggests future research directions for sustainability researchers and practitioners.

Collecting and evaluating large volumes of bibliographic metadata aggregated in the WorldCat database: a proposed methodology to overcome challenges

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Vyacheslav I. Zavalin ◽  
Shawne D. Miksa
Keyword(s):  
Data Collection ◽  
Large Scale ◽  
Large Data ◽  
Study Data ◽  
Lessons Learned ◽  
Future Research ◽  
Data Set ◽  
Content Type ◽  
Large Data Set ◽  
Smart Data

Purpose This paper aims to discuss the challenges encountered in collecting, cleaning and analyzing the large data set of bibliographic metadata records in machine-readable cataloging [MARC 21] format. Possible solutions are presented. Design/methodology/approach This mixed method study relied on content analysis and social network analysis. The study examined subject representation in MARC 21 metadata records created in 2020 in WorldCat – the largest international database of “big smart data.” The methodological challenges that were encountered and solutions are examined. Findings In this general review paper with a focus on methodological issues, the discussion of challenges is followed by a discussion of solutions developed and tested as part of this study. Data collection, processing, analysis and visualization are addressed separately. Lessons learned and conclusions related to challenges and solutions for the design of a large-scale study evaluating MARC 21 bibliographic metadata from WorldCat are given. Overall recommendations for the design and implementation of future research are suggested. Originality/value There are no previous publications that address the challenges and solutions of data collection and analysis of WorldCat’s “big smart data” in the form of MARC 21 data. This is the first study to use a large data set to systematically examine MARC 21 library metadata records created after the most recent addition of new fields and subfields to MARC 21 Bibliographic Format standard in 2019 based on resource description and access rules. It is also the first to focus its analyzes on the networks formed by subject terms shared by MARC 21 bibliographic records in a data set extracted from a heterogeneous centralized database WorldCat.

scholarly journals A Fine-Scale Genetic Map for Vervet Monkeys

2020 ◽  
Vol 37 (7) ◽  
pp. 1855-1865
Author(s):  
Susanne P Pfeifer
Keyword(s):  
Genetic Map ◽  
Recombination Rate ◽  
Large Scale ◽  
Dominant Role ◽  
Great Apes ◽  
Future Research ◽  
Rate Variation ◽  
Vervet Monkeys ◽  
Fine Scale ◽  
Data Set

Abstract Despite its important biological role, the evolution of recombination rates remains relatively poorly characterized. This owes, in part, to the lack of high-quality genomic resources to address this question across diverse species. Humans and our closest evolutionary relatives, anthropoid apes, have remained a major focus of large-scale sequencing efforts, and thus recombination rate variation has been comparatively well studied in this group—with earlier work revealing a conservation at the broad- but not the fine-scale. However, in order to better understand the nature of this variation, and the time scales on which substantial modifications occur, it is necessary to take a broader phylogenetic perspective. I here present the first fine-scale genetic map for vervet monkeys based on whole-genome population genetic data from ten individuals and perform a series of comparative analyses with the great apes. The results reveal a number of striking features. First, owing to strong positive correlations with diversity and weak negative correlations with divergence, analyses suggest a dominant role for purifying and background selection in shaping patterns of variation in this species. Second, results support a generally reduced broad-scale recombination rate compared with the great apes, as well as a narrower fraction of the genome in which the majority of recombination events are observed to occur. Taken together, this data set highlights the great necessity of future research to identify genomic features and quantify evolutionary processes that are driving these rate changes across primates.

scholarly journals Revealing Spatial-Temporal Characteristics and Patterns of Urban Travel: A Large-Scale Analysis and Visualization Study with Taxi GPS Data

2019 ◽  
Vol 8 (6) ◽  
pp. 257 ◽  
Author(s):  
Huihui Wang ◽  
Hong Huang ◽  
Xiaoyong Ni ◽  
Weihua Zeng
Keyword(s):  
Large Scale ◽  
Travel Demand ◽  
Chord Diagram ◽  
Future Research ◽  
Trajectory Data ◽  
Temporal Scales ◽  
Data Set ◽  
Ring Road ◽  
Temporal Characteristics ◽  
Taxi Trajectory

Mobility and spatial interaction data have become increasingly available due to the widespread adoption of location-aware technologies. Examples of mobile data include human daily activities, vehicle trajectories, and animal movements. In this study we focus on a special type of mobility data, i.e., origin–destination (OD) pairs, and propose a new adapted chord diagram plot to reveal the urban human travel spatial-temporal characteristics and patterns of a seven-day taxi trajectory data set collected in Beijing; this large scale data set includes approximately 88.5 million trips of anonymous customers. The spatial distribution patterns of the pick-up points (PUPs) and the drop-off points (DOPs) on weekdays and weekends are analyzed first. The maximum of the morning and the evening peaks are at 8:00–10:00 and 17:00–19:00. The morning peaks of taxis are delayed by 0.5–1 h compared with the commuting morning peaks. Second, travel demand, intensity, time, and distance on weekdays and weekends are analyzed to explore human mobility. The travel demand and high-intensity travel of residents in Beijing is mainly concentrated within the 6th Ring Road. The residents who travel long distances (>10 km) and for a long time (>60 min) mainly from outside the 6th Ring Road and the surrounding new towns of Beijing. The circular structure of the travel distance distribution also confirms the single-center urban structure of Beijing. Finally, a new adapted chord diagram plot is proposed to achieve the spatial-temporal scale visualization of taxi trajectory origin–destination (OD) flows. The method can characterize the volume, direction, and properties of OD flows in multiple spatial-temporal scales; it is implemented using a circular visualization package in R (circlize). Through the visualization experiment of taxi GPS trajectory data in Beijing, the results show that the proposed visualization technology is able to characterize the spatial-temporal patterns of trajectory OD flows in multiple spatial-temporal scales. These results are expected to enhance current urban mobility research and suggest some interesting avenues for future research.

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