首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 734 毫秒
1.
Dengue Fever (DF) has been identified by the World Health organization (WHO) as one of the most serious vector-borne infectious diseases in tropical and sub-tropical areas. During 2007, in particular, there were over 2,000 DF cases in Taiwan, which was the highest number of cases in the recorded history of Taiwan epidemics. Most DF studies have focused mainly on temporal DF patterns and its close association with climatic covariates, whereas they have understated spatial DF patterns (spatial dependence and clustering) and composite space–time effects. The present study proposes a spatio-temporal DF prediction approach based on stochastic Bayesian Maximum Entropy (BME) analysis. Core and site-specific knowledge bases are considered, including climate and health datasets under conditions of uncertainty, space–time dependence functions, and a Poisson regression model of climatic variables contributing to DF occurrences in southern Taiwan during 2007. The results show that the DF outbreaks in the study area are highly influenced by climatic conditions. Furthermore, the analysis can provide the required “one-week-ahead” outbreak warnings based on spatio-temporal predictions of DF distributions. Therefore, the proposed approach can provide the Taiwan Disease Control Agency with a valuable tool to timely identify, control, and even efficiently prevent DF spreading across space–time.  相似文献   

2.
A unified approach to environmental systems modeling   总被引：1，自引：0，他引：1  
The paper considers the differences between hypothetico-deductive and inductive modeling: between modelers who put their primary trust in their scientific intuition about the nature of an environmental model and tend to produce quite complex computer simulation models; and those who prefer to rely on the analysis of observational data to identify the simplest form of model that can represent these data. The tension that sometimes arises because of the different philosophical outlooks of these two modeling groups can be harmful because it tends to fractionate the effort that goes into the investigation of important environmental problems, such as global warming. In an attempt to improve this situation, the paper will outline a new Data-Based Mechanistic (DBM) approach to modeling that tries to meld together the best aspects of these two modeling philosophies in order to develop a unified approach that combines the hypothetico-deductive virtues of good scientific intuition and simulation modeling with the pragmatism of inductive data-based modeling, where more objective inference from data is the primary driving force. In particular, it demonstrates the feasibility of a new method for complex simulation model emulation, in which the methodological tools of DBM modeling are used to develop a reduced dynamic order model that represents the ‘dominant modes’ of the complex simulation model. In this form, the ‘dynamic emulation’ model can be compared with the DBM model obtained directly from the analysis of real data and any tensions between the two modeling approaches may be relaxed to produce models that suit multiple modeling objectives.  相似文献   

3.
This paper describes the spatiotemporal epistematics knowledge synthesis and graphical user interface (SEKS–GUI) framework and its application in medical geography problems. Based on sound theoretical reasoning, the interactive software library of SEKS–GUI explores heterogeneous (spatially non-homogeneous and temporally non-stationary) health attribute distributions (disease incidence, mortality, human exposure, epidemic propagation etc.); expresses the health system’s dependence structure using (ordinary and generalized) spatiotemporal covariance models; synthesizes core knowledge bases, empirical evidence and multi-sourced system uncertainty; and generates a meaningful picture of the real-world system using space–time dependent probability functions and associated maps of health attributes. The implementation stages of the SEKS–GUI library are described in considerable detail using appropriate screens. The wide applicability of SEKS–GUI is demonstrated by reviewing a selection of real-world case studies. An erratum to this article can be found at  相似文献   

4.
Risk perception plays a crucial role in shaping health-related behaviors in a variety of infectious disease control settings. The purpose of this study was to assess risk perception and behavioral changes in response to influenza epidemics. We present a risk perception assessment model that uses information theory linking with a probabilistic risk model to investigate the interplay between risk perception spread and health behavioral changes for an influenza outbreak. Building on human influenza data, we predicted risk perception spread as the amount of risk information. A negative feedback-based information model was used to explore whether health behavioral changes can increase the control effectiveness. Finally, a probabilistic risk assessment framework was used to predict influenza infection risk based on maximal information-derived risk perception. We found that (i) an individual who perceived more accurate knowledge of influenza can substantially increase the amount of mutual risk perception information, (ii) an intervening network over which individuals communicate overlap can be more effective in risk perception transfer, (iii) collective individual responses can increase risk perception information transferred, but may be limited by contact numbers of infectious individuals, and (iv) higher mutual risk perception information gains lower infection risk probability. We also revealed that when people increased information about the benefits of vaccination and antiviral drug used, future infections could significantly be prevented. We suggest that increasing mutual risk perception information through a negative feedback mechanism plays an important role in adaptation and mitigation behavior and policy support.  相似文献   

5.
  相似文献   

6.
Model identification for hydrological forecasting under uncertainty   总被引：2，自引：2，他引：2  
Methods for the identification of models for hydrological forecasting have to consider the specific nature of these models and the uncertainties present in the modeling process. Current approaches fail to fully incorporate these two aspects. In this paper we review the nature of hydrological models and the consequences of this nature for the task of model identification. We then continue to discuss the history (“The need for more POWER‘’), the current state (“Learning from other fields”) and the future (“Towards a general framework”) of model identification. The discussion closes with a list of desirable features for an identification framework under uncertainty and open research questions in need of answers before such a framework can be implemented.  相似文献   

7.
Extreme environmental events have considerable impacts on society. Preparation to mitigate or forecast accurately these events is a growing concern for governments. In this regard, policy and decision makers require accurate tools for risk estimation in order to take informed decisions. This work proposes a Bayesian framework for a unified treatment and statistical modeling of the main components of risk: hazard, vulnerability and exposure. Risk is defined as the expected economic loss or population affected as a consequence of a hazard event. The vulnerability is interpreted as the loss experienced by an exposed population due to hazard events. The framework combines data of different spatial and temporal supports. It produces a sequence of temporal risk maps for the domain of interest including a measure of uncertainty for the hazard and vulnerability. In particular, the considered hazard (rainfall) is interpolated from point-based measured rainfall data using a hierarchical spatio-temporal Kriging model, whose parameters are estimated using the Bayesian paradigm. Vulnerability is modeled using zero-inflated distributions with parameters dependent on climatic variables at local and large scales. Exposure is defined as the total population settled in the spatial domain and is interpolated using census data. The proposed methodology was applied to the Vargas state of Venezuela to map the spatio-temporal risk for the period 1970–2006. The framework highlights both high and low risk areas given extreme rainfall events.  相似文献   

8.
Impact of global change on transmission of human infectious diseases   总被引：1，自引：0，他引：1  
Global change,which refers to large-scale changes in the earth system and human society,has been changing the outbreak and transmission mode of many infectious diseases.Climate change affects infectious diseases directly and indirectly.Meteorological factors including temperature,precipitation,humidity and radiation influence infectious disease by modulating pathogen,host and transmission pathways.Meteorological disasters such as droughts and floods directly impact the outbreak and transmission of infectious diseases.Climate change indirectly impacts infectious diseases by altering the ecological system,including its underlying surface and vegetation distribution.In addition,anthropogenic activities are a driving force for climate change and an indirect forcing of infectious disease transmission.International travel and rural-urban migration are a root cause of infectious disease transmission.Rapid urbanization along with poor infrastructure and high disease risk in the rural-urban fringe has been changing the pattern of disease outbreaks and mortality.Land use changes,such as agricultural expansion and deforestation,have already changed the transmission of infectious disease.Accelerated air,road and rail transportation development may not only increase the transmission speed of outbreaks,but also enlarge the scope of transmission area.In addition,more frequent trade and other economic activities will also increase the potential risks of disease outbreaks and facilitate the spread of infectious diseases.  相似文献   

9.
This comparative review of three assessment reports, the Intergovernmental Panel on Climate Change, (IPCC), The National Research Council (NRC), and United States Global Change Research Program (USGCRP), respectively is presented in response to comments in the press suggesting that the three reports varied substantially in their assessments of associations between global climate and infectious disease in humans. Comparisons of the assessment teams, approach, reports' findings, views on predictive modeling, recommendations to policymakers and future research are presented. All teams were interdisciplinary, two international, one US-based. Although their approaches differed somewhat, all addressed the role of climate change, El Niño and climate variability, and ultimately, human health, especially infectious disease. The panels agreed that a paucity of long-term data and complexity of relationships among factors affecting climate variability and change and human health rendered projections of current predictive models inadequate as the basis for policy decisions. Each team suggested further study of associations among climate variability/climate change and human infectious disease and downscaled models to project regional and subregional outcomes. Each added additional areas for investigation, e.g., mathematical modeling, effects of socioeconomic factors, emergence of zoonotic disease in humans, transmission dynamics of disease agents. Rather than disagreements, there were differences in emphasis on known components and on hypothesized additional contributing factors and relationships among climate and human infectious disease variables.  相似文献   

10.
An estimate of the interval between successive infections is essential for surveillance, control, and modeling of infectious diseases. This paper proposes a method for determining the serial interval when the location and time of onset of illness are known. The theoretical underpinning of this method is the intrinsically spatial nature of disease transmission. Successive infections tend to be closer than unrelated cases of disease and, therefore, exhibit spatial clustering. An incremental Knox type analysis of cases is introduced. Cases occurring at a range of time intervals are examined to determine the serial interval. The significance of clustering is determined using a permutation approach under the null hypothesis of space-time independence. The power of this method is evaluated using an individual level, spatially explicit epidemic simulation. The time increment Knox test is robust to multiple introductions and incomplete sampling. Finally, the increment Knox statistic is used to analyze an outbreak of dengue fever in the city of Florida, Puerto Rico during 1991. Results indicate that the likely interval between successive cases during this outbreak is at least 18–19 days.  相似文献   

11.
We describe an early warning indicator for monitoring infectious diseases. The approach is illustrated with data from a major sheep pox epidemic, which occurred in the Evros prefecture of Greece, from August 2013 until the end of 2014. We present the epidemic data and identify factors affecting this major epidemic using a suitable methodological framework for the sequential analysis of such outbreaks. Environmental conditions and seasonality affect the spread of the epidemic: autumn seems to enhance disease occurrence and higher average temperatures facilitate disease spread. The on-line prediction of the disease potential is investigated through an early warning system that is based on the probability of the disease going extinct. The temporal stability of this indicator is extensively explored.  相似文献   

12.
目的:通过对6例已确诊新型冠状病毒肺炎(COVI-19)患者的确诊过程以及当前疫情防控进行分析和思考,增强民众和医院对新型冠状病毒肺炎和突发公共卫生事件的认识和防控能力;方法:对患者的流行病学史、既往病史、本次疾病诊治过程进行详细调查和记录,查阅相关文献资料,调查疫情对个人及公共卫生的影响。结果:患者经实验室检查、胸部CT检查及咽拭子核酸检查,确诊为新型冠状病毒肺炎,及时对患者进行隔离治疗,多名接触医务人员进行隔离观察。结论:此次疫情发病急、流行快,人群普遍易感;从个人、医院及公共卫生多个方面均应提高对疫情的认识,加强防控措施,保障公共卫生安全。   相似文献   

13.
Supported by the recent advancement of experimental test methods, numerical simulation, and high‐speed communication networks, it is possible to distribute geographically the testing of structural systems using hybrid experimental–computational simulation. One of the barriers for this advanced testing is the lack of flexible software for hybrid simulation using heterogeneous experimental equipment. To address this need, an object‐oriented software framework is designed, developed, implemented, and demonstrated for distributed experimental–computational simulation of structural systems. The software computes the imposed displacements for a range of test methods and co‐ordinates the control of local and distributed configurations of experimental equipment. The object‐oriented design of the software promotes the sharing of modules for experimental equipment, test set‐ups, simulation models, and test methods. The communication model for distributed hybrid testing is similar to that used for parallel computing to solve structural simulation problems. As a demonstration, a distributed pseudodynamic test was conducted using a client–server approach, in which the server program controlled the test equipment in Japan and the client program performed the computational simulation in the United States. The distributed hybrid simulation showed that the software framework is flexible and reliable. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

14.
A typical model of the source of a tsunami (“macroseismic source”) is suggested for use in approximate estimation of maximum tsunami height using straightforward numerical modeling. In this paper the model is tested using three actual events: the 1952 North Kuril Is., 1971 Moneron, and 1994 Shikotan earthquakes, which excited considerable tsunamis at Russia’s Far East coasts. Comparison of the maximum tsunami runup values as obtained in numerical experiments with observations of actual tsunamis showed that the numerical model proposed here is suitable for crude estimation of tsunami runup and tsunami waiting times for coastal population centers in the near zone of a tsunami source.  相似文献   

15.
The Cumulative and Aggregate Simulation of Exposure (CASE) framework is an innovative simulation tool for exploring non-dietary exposures to environmental contaminants. Built upon the Dermal Exposure Reduction Model (DERM) and established methods for collecting detailed human activity patterns, the CASE framework improves upon its predecessor. Although prompted in part by the Food Quality Protection Act of 1996 and the need to assess aggregate exposure to pesticides, the framework was designed to be flexible enough to assess exposure to other contaminants. This paper examines features of the CASE framework in an illustrative application estimating children’s dermal and non-dietary ingestion exposure to lead in the residential environment. Concentration values in various media are taken from a nationwide study and exposure factors are obtained from the literature. Activity pattern input includes sequential micro-level activities collected for 20 children (ages 1 through 6). Modeled results are explored via classification trees and sensitivity analysis. Results of each exposure route are also compared to independent data. Median dermal exposure estimates were 589 and 558 μg/m3 for the right and left hands, respectively, with the resulting output most sensitive to exposure factor terms. The simulation estimated a median non-dietary ingestion rate of 9.5 μg of lead per day with estimates most sensitive to the surface area of mouthed objects.  相似文献   

16.
2.5-D modeling and inversion techniques are much closer to reality than the simple and traditional 2-D seismic wave modeling and inversion. The sensitivity kernels required in full waveform seismic tomographic inversion are the Fréchet derivatives of the displacement vector with respect to the independent anisotropic model parameters of the subsurface. They give the sensitivity of the seismograms to changes in the model parameters. This paper applies two methods, called ‘the perturbation method’ and ‘the matrix method’, to derive the sensitivity kernels for 2.5-D seismic waveform inversion. We show that the two methods yield the same explicit expressions for the Fréchet derivatives using a constant-block model parameterization, and are available for both the line-source (2-D) and the point-source (2.5-D) cases. The method involves two Green’s function vectors and their gradients, as well as the derivatives of the elastic modulus tensor with respect to the independent model parameters. The two Green’s function vectors are the responses of the displacement vector to the two directed unit vectors located at the source and geophone positions, respectively; they can be generally obtained by numerical methods. The gradients of the Green’s function vectors may be approximated in the same manner as the differential computations in the forward modeling. The derivatives of the elastic modulus tensor with respect to the independent model parameters can be obtained analytically, dependent on the class of medium anisotropy. Explicit expressions are given for two special cases—isotropic and tilted transversely isotropic (TTI) media. Numerical examples are given for the latter case, which involves five independent elastic moduli (or Thomsen parameters) plus one angle defining the symmetry axis.  相似文献   

17.
Specific features of the bottom topography structure and the character of morphostructural segmentation of the rift zone of the Reykjanes Ridge change substantially along the ridge strike with increasing distance from Iceland’s hotspot. A clearly pronounced regularity of changes is observed in the rift zone’s morphology from the axial uplift (in the northern part of the ridge) to the rift valleys (in the southern part of the ridge) through an intermediate or transitional type of morphology. The results of numerical modeling showed that changes in the rift zone’s morphology along the Reykjanes Ridge strike are largely caused by changes in the degree of mantle heating and depend on the intensity of magma supply. It is shown that under conditions of ultraslow spreading, it is these parameters that control the presence or absence of crustal magma chambers, as well as the thickness of the effectively-elastic layer of the axial lithosphere. The experimental modeling of topography-forming deformations and structuring on the Reykjanes Ridge showed that under oblique extension, specific features of the formation of axial fractures and the character of their segmentation mainly depend on the thickness of the axial lithosphere, its heating zone width, and the kinematics of spreading. The experiments also showed that the tendency of fractures to develop obliquely to the extension axis is caused by the action of the inclined zone of the location of the deformation, and shear deformations play a substantial role in the lithosphere’s destruction as the inclination angle increases.  相似文献   

18.
Nevado del Huila, a glacier-covered volcano in the South of Colombia’s Cordillera Central, had not experienced any historical eruptions before 2007. In 2007 and 2008, the volcano erupted with phreatic and phreatomagmatic events which produced lahars with flow volumes of up to about 300 million m3 causing severe damage to infrastructure and loss of lives. The magnitude of these lahars and the prevailing potential for similar or even larger events, poses significant hazards to local people and makes appropriate modeling a real challenge. In this study, we analyze the recent lahars to better understand the main processes and then model possible scenarios for future events. We used lahar inundation depths, travel duration, and flow deposits to constrain the dimensions of the 2007 event and applied LAHARZ and FLO-2D for lahar modeling. Measured hydrographs, geophone seismic sensor data and calculated peak discharges served as input data for the reconstruction of flow hydrographs and for calibration of the models. For model validation, results were compared with field data collected along the Páez and Simbola Rivers. Based on the results of the 2007 lahar simulation, we modeled lahar scenarios with volumes between 300 million and 1 billion m3. The approach presented here represents a feasible solution for modeling high-magnitude flows like lahars and allows an assessment of potential future events and related consequences for population centers downstream of Nevado del Huila.  相似文献   

19.
Neural networks are universal approximators for nonlinear functions. This study aimed to develop an algorithm for functional link artificial neural network (FLANN), and to simulate insect’s food intake dynamics using the algorithm. Complete Matlab codes for FLANN algorithm were given in the paper. Conventional models and FLANN were used to modeling accumulated food intake of the larva of a holometabolous insect, Spodoptera litura. Simulation performance of FLANN was compared against conventional models and sensitivity analysis was conducted on FLANN. The results showed that the FLANN algorithm performed better than conventional models in the simulation of dynamics and temperature–time dependent relationship of larva’s food intake. The conventional models like fractional function, polynomial function, and exponential function were indicated to simulate the food intake dynamics at a higher accuracy but their performances were worse than FLANN. Both multivariate linear regression and trend surface model were used to describe temperature–time dependent relationship of food intake. The overall trend for this relationship could be simulated using these models, however, the simulation accuracy of these models was lower than FLANN. Sensitivity analysis showed that Legendre functions, Chebyshov functions, and trigonometric functions, used as the basis functions in FLANN, yielded better fitness than Laguerre functions and Hermite functions. The mean squared error of simulation using Legendre functions, Chebyshov functions, and trigonometric functions decreased as the increase of the number of these basis functions. Simulation performance also varied with the change of type of nonlinear functions and parameter values in the function. Linear function, negative exponential function and power function were the best nonlinear functions, which yielded more stable outputs as the change of parameter values.  相似文献   

20.
Industrial pollution has caused serious human health risk because the pollutants can be accumulated in human body via multi routes in a long term, especially in areas of rapid industrialization. It is of great importance to obtain the pollutants’ information, including the transport routes and spatial distribution in the various environmental media of different sub-regions, to facilitate more accurate risk assessment and more effective risk management in urban ecosystems. In this article, we proposed a research framework of urban ecological risk assessment method, which combines the multimedia fugacity model, the multi-route exposure model, exposure-risk relationships and geographic information system (GIS). An urban ecological risk assessment of a hypothetical region indicates that it is possible and feasible to introduce GIS into the previous method to satisfy the requirements of risk management. The assessment results can be further utilized for industrial pollution emission control.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号