A Stochastic Model for Malaria Transmission Dynamics
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Rachel Waema Mbogo
2018-01-01
Full Text Available Malaria is one of the three most dangerous infectious diseases worldwide (along with HIV/AIDS and tuberculosis. In this paper we compare the disease dynamics of the deterministic and stochastic models in order to determine the effect of randomness in malaria transmission dynamics. Relationships between the basic reproduction number for malaria transmission dynamics between humans and mosquitoes and the extinction thresholds of corresponding continuous-time Markov chain models are derived under certain assumptions. The stochastic model is formulated using the continuous-time discrete state Galton-Watson branching process (CTDSGWbp. The reproduction number of deterministic models is an essential quantity to predict whether an epidemic will spread or die out. Thresholds for disease extinction from stochastic models contribute crucial knowledge on disease control and elimination and mitigation of infectious diseases. Analytical and numerical results show some significant differences in model predictions between the stochastic and deterministic models. In particular, we find that malaria outbreak is more likely if the disease is introduced by infected mosquitoes as opposed to infected humans. These insights demonstrate the importance of a policy or intervention focusing on controlling the infected mosquito population if the control of malaria is to be realized.
Chancroid transmission dynamics: a mathematical modeling approach.
Bhunu, C P; Mushayabasa, S
2011-12-01
Mathematical models have long been used to better understand disease transmission dynamics and how to effectively control them. Here, a chancroid infection model is presented and analyzed. The disease-free equilibrium is shown to be globally asymptotically stable when the reproduction number is less than unity. High levels of treatment are shown to reduce the reproduction number suggesting that treatment has the potential to control chancroid infections in any given community. This result is also supported by numerical simulations which show a decline in chancroid cases whenever the reproduction number is less than unity.
Nonlinear dynamics modelling of multistage micro-planetary gear transmission
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Li Jianying
2018-01-01
Full Text Available The transmission structure of a 2K-H multistage micro-planetary gear transmission reducer is described in detail, and three assumptions are supposed in dynamic modelling. On basis of these assumptions, a three stages 2K-H micro-planetary gear transmission dynamic model is established, in which the relative displacement each meshing gear pairs can be obtained after including the comprehensive transmission error. According to gear kinematics, the friction arms between the sun gear, the ring gear and the nth planet are also obtained, and the friction coefficient in the mixed elastohydrodynamic lubrication is considered, the transmission system motion differential equations are obtained, including above factors and the time-varying meshing stiffness, damping and backlash, inter-stage coupling stiffness, it can be provided an theoretical foundation for further analysing the parameter sensitivity, dynamic stability and designing.
Dynamic queuing transmission model for dynamic network loading
DEFF Research Database (Denmark)
Raovic, Nevena; Nielsen, Otto Anker; Prato, Carlo Giacomo
2017-01-01
and allowing for the representation of multiple vehicle classes, queue spillbacks and shock waves. The model assumes that a link is split into a moving part plus a queuing part, and p that traffic dynamics are given by a triangular fundamental diagram. A case-study is investigated and the DQTM is compared...
Lossy transmission line model of hydrofractured well dynamics
Energy Technology Data Exchange (ETDEWEB)
Patzek, T.W. [Department of Materials Science and Mineral Engineering, University of California at Berkeley, Berkeley, CA (United States); De, A. [Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States)
2000-01-01
The real-time detection of hydrofracture growth is crucial to the successful operation of water, CO{sub 2} or steam injection wells in low-permeability reservoirs and to the prevention of subsidence and well failure. In this paper, we describe propagation of very low frequency (1-10 to 100 Hz) Stoneley waves in a fluid-filled wellbore and their interactions with the fundamental wave mode in a vertical hydrofracture. We demonstrate that Stoneley-wave loses energy to the fracture and the energy transfer from the wellbore to the fracture opening is most efficient in soft rocks. We conclude that placing the wave source and receivers beneath the injection packer provides the most efficient means of hydrofracture monitoring. We then present the lossy transmission line model of wellbore and fracture for the detection and characterization of fracture state and volume. We show that this model captures the wellbore and fracture geometry, the physical properties of injected fluid and the wellbore-fracture system dynamics. The model is then compared with experimentally measured well responses. The simulated responses are in good agreement with published experimental data from several water injection wells with depths ranging from 1000 ft to 9000 ft. Hence, we conclude that the transmission line model of water injectors adequately captures wellbore and fracture dynamics. Using an extensive data set for the South Belridge Diatomite waterfloods, we demonstrate that even for very shallow wells the fracture size and state can be adequately recognized at wellhead. Finally, we simulate the effects of hydrofracture extension on the transient response to a pulse signal generated at wellhead. We show that hydrofracture extensions can indeed be detected by monitoring the wellhead pressure at sufficiently low frequencies.
Dynamics Modelling of Transmission Gear Rattle and Analysis on Influence Factors
He, Xiaona; Zhang, Honghui
2018-02-01
Based on the vibration dynamics modeling for the single stage gear of transmission system, this paper is to understand the mechanism of transmission rattle. The dynamic model response using MATLAB and Runge-Kutta algorithm is analyzed, and the ways for reducing the rattle noise of the automotive transmission is summarized.
Mathematical Modelling of Bacterial Meningitis Transmission Dynamics with Control Measures
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Joshua Kiddy K. Asamoah
2018-01-01
Full Text Available Vaccination and treatment are the most effective ways of controlling the transmission of most infectious diseases. While vaccination helps susceptible individuals to build either a long-term immunity or short-term immunity, treatment reduces the number of disease-induced deaths and the number of infectious individuals in a community/nation. In this paper, a nonlinear deterministic model with time-dependent controls has been proposed to describe the dynamics of bacterial meningitis in a population. The model is shown to exhibit a unique globally asymptotically stable disease-free equilibrium E0, when the effective reproduction number RVT≤1, and a globally asymptotically stable endemic equilibrium E1, when RVT>1; and it exhibits a transcritical bifurcation at RVT=1. Carriers have been shown (by Tornado plot to have a higher chance of spreading the infection than those with clinical symptoms who will sometimes be bound to bed during the acute phase of the infection. In order to find the best strategy for minimizing the number of carriers and ill individuals and the cost of control implementation, an optimal control problem is set up by defining a Lagrangian function L to be minimized subject to the proposed model. Numerical simulation of the optimal problem demonstrates that the best strategy to control bacterial meningitis is to combine vaccination with other interventions (such as treatment and public health education. Additionally, this research suggests that stakeholders should press hard for the production of existing/new vaccines and antibiotics and their disbursement to areas that are most affected by bacterial meningitis, especially Sub-Saharan Africa; furthermore, individuals who live in communities where the environment is relatively warm (hot/moisture are advised to go for vaccination against bacterial meningitis.
Modelling of Rabies Transmission Dynamics Using Optimal Control Analysis
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Joshua Kiddy K. Asamoah
2017-01-01
Full Text Available We examine an optimal way of eradicating rabies transmission from dogs into the human population, using preexposure prophylaxis (vaccination and postexposure prophylaxis (treatment due to public education. We obtain the disease-free equilibrium, the endemic equilibrium, the stability, and the sensitivity analysis of the optimal control model. Using the Latin hypercube sampling (LHS, the forward-backward sweep scheme and the fourth-order Range-Kutta numerical method predict that the global alliance for rabies control’s aim of working to eliminate deaths from canine rabies by 2030 is attainable through mass vaccination of susceptible dogs and continuous use of pre- and postexposure prophylaxis in humans.
Analyzing the Dynamics of a Rumor Transmission Model with Incubation
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Liang'an Huo
2012-01-01
Full Text Available This paper considers a rumor transmission model with incubation that incorporates constant recruitment and has infectious force in the latent period and infected period. By carrying out a global analysis of the model and studying the stability of the rumor-free equilibrium and the rumor-endemic equilibrium, we use the geometric approach for ordinary differential equations which is based on the use of higher-order generalization of Bendixson’s criterion. It shows that either the number of rumor infective individuals tends to zero as time evolves or the rumor persists. We prove that the transcritical bifurcation occurs at R0 crosses the bifurcation threshold R0=1 by projecting the flow onto the extended center manifold. Since the rumor endemic level at the equilibrium is a continuous function of R0, as a consequence for successful eradication of the rumor, one should simply reduce R0 continuously below the threshold value 1. Finally, the obtained results are numerically validated and then discussed from both the mathematical and the sociological perspectives.
Institute of Scientific and Technical Information of China (English)
呼义翔; 雷天时; 吴撼宇; 郭宁; 韩娟娟; 邱爱慈; 王亮平; 黄涛; 丛培天; 张信军; 李岩; 曾正中; 孙铁平
2011-01-01
The transmission-line-circuit model of the Z accelerator, developed originally by W. A. STYGAR, P. A. CORCORAN, et al., is revised. The revised model uses different calculations for the electron loss and flow impedance in the magnetically insulated transmission line system of the Z accelerator before and after magnetic insulation is established. By including electron pressure and zero electric field at the cathode, a closed set of equations is obtained at each time step, and dynamic shunt resistance （used to represent any electron loss to the anode） and flow impedance are solved, which have been incorporated into the transmission line code for simulations of the vacuum section in the Z accelerator. Finally, the results are discussed in comparison with earlier findings to show the effectiveness and limitations of the model.
Variations in Modeled Dengue Transmission over Puerto Rico Using a Climate Driven Dynamic Model
Morin, Cory; Monaghan, Andrew; Crosson, William; Quattrochi, Dale; Luvall, Jeffrey
2014-01-01
Dengue fever is a mosquito-borne viral disease reemerging throughout much of the tropical Americas. Dengue virus transmission is explicitly influenced by climate and the environment through its primary vector, Aedes aegypti. Temperature regulates Ae. aegypti development, survival, and replication rates as well as the incubation period of the virus within the mosquito. Precipitation provides water for many of the preferred breeding habitats of the mosquito, including buckets, old tires, and other places water can collect. Because of variations in topography, ocean influences and atmospheric processes, temperature and rainfall patterns vary across Puerto Rico and so do dengue virus transmission rates. Using NASA's TRMM (Tropical Rainfall Measuring Mission) satellite for precipitation input, ground-based observations for temperature input, and laboratory confirmed dengue cases reported by the Centers for Disease Control and Prevention for parameter calibration, we modeled dengue transmission at the county level across Puerto Rico from 2010-2013 using a dynamic dengue transmission model that includes interacting vector ecology and epidemiological components. Employing a Monte Carlo approach, we performed ensembles of several thousands of model simulations for each county in order to resolve the model uncertainty arising from using different combinations of parameter values that are not well known. The top 1% of model simulations that best reproduced the reported dengue case data were then analyzed to determine the most important parameters for dengue virus transmission in each county, as well as the relative influence of climate variability on transmission. These results can be used by public health workers to implement dengue control methods that are targeted for specific locations and climate conditions.
Dynamic modeling of fluid power transmissions for wind turbines
Diepeveen, N.F.B.; Jarquin Laguna, A.
2011-01-01
Fluid power transmission for wind turbines is quietly gaining more ground/interest. The principle of the various concepts presented so far is to convert aerodynamic torque of the rotor blades into a pressurized fluid flow by means of a positive displacement pump. At the other end of the fluid power
Modeling the transmission dynamics of Ebola virus disease in Liberia.
Xia, Zhi-Qiang; Wang, Shi-Fu; Li, Shen-Long; Huang, Liu-Yu; Zhang, Wen-Yi; Sun, Gui-Quan; Gai, Zhong-Tao; Jin, Zhen
2015-09-08
Ebola virus disease (EVD) has erupted many times in some zones since it was first found in 1976. The 2014 EVD outbreak in West Africa is the largest ever, which has caused a large number of deaths and the most serious country is Liberia during the outbreak period. Based on the data released by World Health Organization and the actual transmission situations, we investigate the impact of different transmission routes on the EVD outbreak in Liberia and estimate the basic reproduction number R0 = 2.012 in the absence of effective control measures. Through sensitivity and uncertainty analysis, we reveal that the transmission coefficients of suspected and probable cases have stronger correlations on the basic reproduction number. Furthermore, we study the influence of control measures (isolation and safe burial measures) on EVD outbreak. It is found that if combined control measures are taken, the basic reproduction number will be less than one and thus EVD in Liberia may be well contained. The obtained results may provide new guidance to prevent and control the spread of disease.
Threshold Dynamics of a Stochastic SIR Model with Vertical Transmission and Vaccination
Miao, Anqi; Zhang, Jian; Zhang, Tongqian; Pradeep, B. G. Sampath Aruna
2017-01-01
A stochastic SIR model with vertical transmission and vaccination is proposed and investigated in this paper. The threshold dynamics are explored when the noise is small. The conditions for the extinction or persistence of infectious diseases are deduced. Our results show that large noise can lead to the extinction of infectious diseases which is conducive to epidemic diseases control.
Threshold Dynamics of a Stochastic SIR Model with Vertical Transmission and Vaccination
Directory of Open Access Journals (Sweden)
Anqi Miao
2017-01-01
Full Text Available A stochastic SIR model with vertical transmission and vaccination is proposed and investigated in this paper. The threshold dynamics are explored when the noise is small. The conditions for the extinction or persistence of infectious diseases are deduced. Our results show that large noise can lead to the extinction of infectious diseases which is conducive to epidemic diseases control.
Springer, Andrea; Kappeler, Peter M; Nunn, Charles L
2017-05-01
Social networks provide an established tool to implement heterogeneous contact structures in epidemiological models. Dynamic temporal changes in contact structure and ranging behaviour of wildlife may impact disease dynamics. A consensus has yet to emerge, however, concerning the conditions in which network dynamics impact model outcomes, as compared to static approximations that average contact rates over longer time periods. Furthermore, as many pathogens can be transmitted both environmentally and via close contact, it is important to investigate the relative influence of both transmission routes in real-world populations. Here, we use empirically derived networks from a population of wild primates, Verreaux's sifakas (Propithecus verreauxi), and simulated networks to investigate pathogen spread in dynamic vs. static social networks. First, we constructed a susceptible-exposed-infected-recovered model of Cryptosporidium spread in wild Verreaux's sifakas. We incorporated social and environmental transmission routes and parameterized the model for two different climatic seasons. Second, we used simulated networks and greater variation in epidemiological parameters to investigate the conditions in which dynamic networks produce larger outbreak sizes than static networks. We found that average outbreak size of Cryptosporidium infections in sifakas was larger when the disease was introduced in the dry season than in the wet season, driven by an increase in home range overlap towards the end of the dry season. Regardless of season, dynamic networks always produced larger average outbreak sizes than static networks. Larger outbreaks in dynamic models based on simulated networks occurred especially when the probability of transmission and recovery were low. Variation in tie strength in the dynamic networks also had a major impact on outbreak size, while network modularity had a weaker influence than epidemiological parameters that determine transmission and recovery
Directory of Open Access Journals (Sweden)
Mathieu Andraud
Full Text Available Dengue is a vector-borne disease recognized as the major arbovirose with four immunologically distant dengue serotypes coexisting in many endemic areas. Several mathematical models have been developed to understand the transmission dynamics of dengue, including the role of cross-reactive antibodies for the four different dengue serotypes. We aimed to review deterministic models of dengue transmission, in order to summarize the evolution of insights for, and provided by, such models, and to identify important characteristics for future model development. We identified relevant publications using PubMed and ISI Web of Knowledge, focusing on mathematical deterministic models of dengue transmission. Model assumptions were systematically extracted from each reviewed model structure, and were linked with their underlying epidemiological concepts. After defining common terms in vector-borne disease modelling, we generally categorised fourty-two published models of interest into single serotype and multiserotype models. The multi-serotype models assumed either vector-host or direct host-to-host transmission (ignoring the vector component. For each approach, we discussed the underlying structural and parameter assumptions, threshold behaviour and the projected impact of interventions. In view of the expected availability of dengue vaccines, modelling approaches will increasingly focus on the effectiveness and cost-effectiveness of vaccination options. For this purpose, the level of representation of the vector and host populations seems pivotal. Since vector-host transmission models would be required for projections of combined vaccination and vector control interventions, we advocate their use as most relevant to advice health policy in the future. The limited understanding of the factors which influence dengue transmission as well as limited data availability remain important concerns when applying dengue models to real-world decision problems.
A review of typhoid fever transmission dynamic models and economic evaluations of vaccination.
Watson, Conall H; Edmunds, W John
2015-06-19
Despite a recommendation by the World Health Organization (WHO) that typhoid vaccines be considered for the control of endemic disease and outbreaks, programmatic use remains limited. Transmission models and economic evaluation may be informative in decision making about vaccine programme introductions and their role alongside other control measures. A literature search found few typhoid transmission models or economic evaluations relative to analyses of other infectious diseases of similar or lower health burden. Modelling suggests vaccines alone are unlikely to eliminate endemic disease in the short to medium term without measures to reduce transmission from asymptomatic carriage. The single identified data-fitted transmission model of typhoid vaccination suggests vaccines can reduce disease burden substantially when introduced programmatically but that indirect protection depends on the relative contribution of carriage to transmission in a given setting. This is an important source of epidemiological uncertainty, alongside the extent and nature of natural immunity. Economic evaluations suggest that typhoid vaccination can be cost-saving to health services if incidence is extremely high and cost-effective in other high-incidence situations, when compared to WHO norms. Targeting vaccination to the highest incidence age-groups is likely to improve cost-effectiveness substantially. Economic perspective and vaccine costs substantially affect estimates, with disease incidence, case-fatality rates, and vaccine efficacy over time also important determinants of cost-effectiveness and sources of uncertainty. Static economic models may under-estimate benefits of typhoid vaccination by omitting indirect protection. Typhoid fever transmission models currently require per-setting epidemiological parameterisation to inform their use in economic evaluation, which may limit their generalisability. We found no economic evaluation based on transmission dynamic modelling, and no
Dynamic Strategic Information Transmission
Mikhail Golosov; Vasiliki Skreta; Aleh Tsyvinski; Andrea Wilson
2011-01-01
This paper studies strategic information transmission in a dynamic environment where, each period, a privately informed expert sends a message and a decision maker takes an action. Our main result is that, in contrast to a static environment, full information revelation is possible. The gradual revelation of information and the eventual full revelation is supported by the dynamic rewards and punishments. The construction of a fully revealing equilibrium relies on two key features. The first f...
Dynamical behavior of an epidemic model for a vector-borne disease with direct transmission
International Nuclear Information System (INIS)
Cai Liming; Li Xuezhi; Li Zhaoqiang
2013-01-01
An epidemic model of a vector-borne disease with direct transmission is investigated. The reproduction number (R 0 ) of the model is obtained. Rigorous qualitative analysis of the model reveals the presence of the phenomenon of backward bifurcation (where the stable disease-free equilibrium (DFE) coexists with a stable endemic equilibrium when the reproduction number of the disease is less than unity) in the standard incidence model. The phenomenon shows that the classical epidemiological requirement of having the reproduction number less than unity is no longer sufficient, although necessary, for effectively controlling the spread of some vector-borne diseases in a community. The backward bifurcation phenomenon can be removed by substituting the standard incidence with a bilinear mass action incidence. By using Lyapunov function theory and LaSalle invariance principle, it is shown that the unique endemic equilibrium for the model with a mass action incidence is globally stable if the reproduction number R mass is greater than one in feasible region. This suggests that the use of standard incidence in modelling some vector-borne diseases with direct transmission results in the presence of backward bifurcation. Numerical simulations analyze the effect of the direct transmission and the disease-induced death rate on dynamics of the disease transmission, and also verify our analyzed results.
Frerichs, Leah M; Araz, Ozgur M; Huang, Terry T-K
2013-01-01
Research evidence indicates that obesity has spread through social networks, but lever points for interventions based on overlapping networks are not well studied. The objective of our research was to construct and parameterize a system dynamics model of the social transmission of behaviors through adult and youth influence in order to explore hypotheses and identify plausible lever points for future childhood obesity intervention research. Our objectives were: (1) to assess the sensitivity of childhood overweight and obesity prevalence to peer and adult social transmission rates, and (2) to test the effect of combinations of prevention and treatment interventions on the prevalence of childhood overweight and obesity. To address the first objective, we conducted two-way sensitivity analyses of adult-to-child and child-to-child social transmission in relation to childhood overweight and obesity prevalence. For the second objective, alternative combinations of prevention and treatment interventions were tested by varying model parameters of social transmission and weight loss behavior rates. Our results indicated child overweight and obesity prevalence might be slightly more sensitive to the same relative change in the adult-to-child compared to the child-to-child social transmission rate. In our simulations, alternatives with treatment alone, compared to prevention alone, reduced the prevalence of childhood overweight and obesity more after 10 years (1.2-1.8% and 0.2-1.0% greater reduction when targeted at children and adults respectively). Also, as the impact of adult interventions on children was increased, the rank of six alternatives that included adults became better (i.e., resulting in lower 10 year childhood overweight and obesity prevalence) than alternatives that only involved children. The findings imply that social transmission dynamics should be considered when designing both prevention and treatment intervention approaches. Finally, targeting adults may
Directory of Open Access Journals (Sweden)
Leah M Frerichs
Full Text Available Research evidence indicates that obesity has spread through social networks, but lever points for interventions based on overlapping networks are not well studied. The objective of our research was to construct and parameterize a system dynamics model of the social transmission of behaviors through adult and youth influence in order to explore hypotheses and identify plausible lever points for future childhood obesity intervention research. Our objectives were: (1 to assess the sensitivity of childhood overweight and obesity prevalence to peer and adult social transmission rates, and (2 to test the effect of combinations of prevention and treatment interventions on the prevalence of childhood overweight and obesity. To address the first objective, we conducted two-way sensitivity analyses of adult-to-child and child-to-child social transmission in relation to childhood overweight and obesity prevalence. For the second objective, alternative combinations of prevention and treatment interventions were tested by varying model parameters of social transmission and weight loss behavior rates. Our results indicated child overweight and obesity prevalence might be slightly more sensitive to the same relative change in the adult-to-child compared to the child-to-child social transmission rate. In our simulations, alternatives with treatment alone, compared to prevention alone, reduced the prevalence of childhood overweight and obesity more after 10 years (1.2-1.8% and 0.2-1.0% greater reduction when targeted at children and adults respectively. Also, as the impact of adult interventions on children was increased, the rank of six alternatives that included adults became better (i.e., resulting in lower 10 year childhood overweight and obesity prevalence than alternatives that only involved children. The findings imply that social transmission dynamics should be considered when designing both prevention and treatment intervention approaches. Finally
Directory of Open Access Journals (Sweden)
Morgan E. Smith
2017-03-01
Full Text Available Mathematical models of parasite transmission provide powerful tools for assessing the impacts of interventions. Owing to complexity and uncertainty, no single model may capture all features of transmission and elimination dynamics. Multi-model ensemble modelling offers a framework to help overcome biases of single models. We report on the development of a first multi-model ensemble of three lymphatic filariasis (LF models (EPIFIL, LYMFASIM, and TRANSFIL, and evaluate its predictive performance in comparison with that of the constituents using calibration and validation data from three case study sites, one each from the three major LF endemic regions: Africa, Southeast Asia and Papua New Guinea (PNG. We assessed the performance of the respective models for predicting the outcomes of annual MDA strategies for various baseline scenarios thought to exemplify the current endemic conditions in the three regions. The results show that the constructed multi-model ensemble outperformed the single models when evaluated across all sites. Single models that best fitted calibration data tended to do less well in simulating the out-of-sample, or validation, intervention data. Scenario modelling results demonstrate that the multi-model ensemble is able to compensate for variance between single models in order to produce more plausible predictions of intervention impacts. Our results highlight the value of an ensemble approach to modelling parasite control dynamics. However, its optimal use will require further methodological improvements as well as consideration of the organizational mechanisms required to ensure that modelling results and data are shared effectively between all stakeholders.
PREDICTION OF DENGUE FEVER EPIDEMIC SPREADING USING DYNAMICS TRANSMISSION VECTOR MODEL
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Retno Widyaningrum
2014-05-01
Full Text Available Increasing number of dengue cases in Surabaya shows that its city has high potential of dengue fever epidemic. Although some policies were designed by Surabaya Health Department, such as fogging and mosquito’s nest eradication, but these efforts still out of target because of inaccurate predictions. Ineffectiveness eradication of dengue fever epidemic is caused by lack of information and knowledge on environmental conditions in Surabaya. Developing spread and prediction system to minimize dengue fever epidemic is necessary to be conducted immediately. Spread and prediction system can improve eradication and prevention accuracy. The transmission dynamics vector simulation will be used as an approach to draw a complex system ofmosquito life cycle in which involve a lot offactors. Dynamics transmission model used to build model in mosquito model (oviposition rate and pre adult mosquito, infected and death cases in dengue fever. The model of mosquito and infected population can represent system. The output of this research is website of spread and prediction system of dengue fever epidemics to predict growth rate of Aedes Aegypti mosquito, infected, and death population because of dengue fever epidemics. The deviation of infected population is 0,519. The model of death cases in dengue fever is less precision with the deviation 1,229. Death cases model need improvement by adding some variables that influence to dengue fever death cases. Spread ofdengue fever prediction will help the government, health department to decide the best policies in minimizing the spread ofdengue fever epidemics.
Global dynamics of multi-group SEI animal disease models with indirect transmission
International Nuclear Information System (INIS)
Wang, Yi; Cao, Jinde
2014-01-01
A challenge to multi-group epidemic models in mathematical epidemiology is the exploration of global dynamics. Here we formulate multi-group SEI animal disease models with indirect transmission via contaminated water. Under biologically motivated assumptions, the basic reproduction number R 0 is derived and established as a sharp threshold that completely determines the global dynamics of the system. In particular, we prove that if R 0 <1, the disease-free equilibrium is globally asymptotically stable, and the disease dies out; whereas if R 0 >1, then the endemic equilibrium is globally asymptotically stable and thus unique, and the disease persists in all groups. Since the weight matrix for weighted digraphs may be reducible, the afore-mentioned approach is not directly applicable to our model. For the proofs we utilize the classical method of Lyapunov, graph-theoretic results developed recently and a new combinatorial identity. Since the multiple transmission pathways may correspond to the real world, the obtained results are of biological significance and possible generalizations of the model are also discussed
Fournié, Guillaume; Pfeiffer, Dirk U; Bendrey, Robin
2017-02-01
Zoonotic pathogens are frequently hypothesized as emerging with the origins of farming, but evidence of this is elusive in the archaeological records. To explore the potential impact of animal domestication on zoonotic disease dynamics and human infection risk, we developed a model simulating the transmission of Brucella melitensis within early domestic goat populations. The model was informed by archaeological data describing goat populations in Neolithic settlements in the Fertile Crescent, and used to assess the potential of these populations to sustain the circulation of Brucella . Results show that the pathogen could have been sustained even at low levels of transmission within these domestic goat populations. This resulted from the creation of dense populations and major changes in demographic characteristics. The selective harvesting of young male goats, likely aimed at improving the efficiency of food production, modified the age and sex structure of these populations, increasing the transmission potential of the pathogen within these populations. Probable interactions between Neolithic settlements would have further promoted pathogen maintenance. By fostering conditions suitable for allowing domestic goats to become reservoirs of Brucella melitensis , the early stages of agricultural development were likely to promote the exposure of humans to this pathogen.
Characterizing measles transmission in India: a dynamic modeling study using verbal autopsy data.
Verguet, Stéphane; Jones, Edward O; Johri, Mira; Morris, Shaun K; Suraweera, Wilson; Gauvreau, Cindy L; Jha, Prabhat; Jit, Mark
2017-08-10
Decreasing trends in measles mortality have been reported in recent years. However, such estimates of measles mortality have depended heavily on assumed regional measles case fatality risks (CFRs) and made little use of mortality data from low- and middle-income countries in general and India, the country with the highest measles burden globally, in particular. We constructed a dynamic model of measles transmission in India with parameters that were empirically inferred using spectral analysis from a time series of measles mortality extracted from the Million Death Study, an ongoing longitudinal study recording deaths across 2.4 million Indian households and attributing causes of death using verbal autopsy. The model was then used to estimate the measles CFR, the number of measles deaths, and the impact of vaccination in 2000-2015 among under-five children in India and in the states of Bihar and Uttar Pradesh (UP), two states with large populations and the highest numbers of measles deaths in India. We obtained the following estimated CFRs among under-five children for the year 2005: 0.63% (95% confidence interval (CI): 0.40-1.00%) for India as a whole, 0.62% (0.38-1.00%) for Bihar, and 1.19% (0.80-1.75%) for UP. During 2000-2015, we estimated that 607,000 (95% CI: 383,000-958,000) under-five deaths attributed to measles occurred in India as a whole. If no routine vaccination or supplemental immunization activities had occurred from 2000 to 2015, an additional 1.6 (1.0-2.6) million deaths for under-five children would have occurred across India. We developed a data- and model-driven estimation of the historical measles dynamics, CFR, and vaccination impact in India, extracting the periodicity of epidemics using spectral and coherence analysis, which allowed us to infer key parameters driving measles transmission dynamics and mortality.
Mathematical modeling of climate change and malaria transmission dynamics: a historical review.
Eikenberry, Steffen E; Gumel, Abba B
2018-04-24
Malaria, one of the greatest historical killers of mankind, continues to claim around half a million lives annually, with almost all deaths occurring in children under the age of five living in tropical Africa. The range of this disease is limited by climate to the warmer regions of the globe, and so anthropogenic global warming (and climate change more broadly) now threatens to alter the geographic area for potential malaria transmission, as both the Plasmodium malaria parasite and Anopheles mosquito vector have highly temperature-dependent lifecycles, while the aquatic immature Anopheles habitats are also strongly dependent upon rainfall and local hydrodynamics. A wide variety of process-based (or mechanistic) mathematical models have thus been proposed for the complex, highly nonlinear weather-driven Anopheles lifecycle and malaria transmission dynamics, but have reached somewhat disparate conclusions as to optimum temperatures for transmission, and the possible effect of increasing temperatures upon (potential) malaria distribution, with some projecting a large increase in the area at risk for malaria, but others predicting primarily a shift in the disease's geographic range. More generally, both global and local environmental changes drove the initial emergence of P. falciparum as a major human pathogen in tropical Africa some 10,000 years ago, and the disease has a long and deep history through the present. It is the goal of this paper to review major aspects of malaria biology, methods for formalizing these into mathematical forms, uncertainties and controversies in proper modeling methodology, and to provide a timeline of some major modeling efforts from the classical works of Sir Ronald Ross and George Macdonald through recent climate-focused modeling studies. Finally, we attempt to place such mathematical work within a broader historical context for the "million-murdering Death" of malaria.
DEFF Research Database (Denmark)
Mortensen, Peter Mølgaard; Jensen, Anker Degn; Hansen, Thomas Willum
2015-01-01
The temperature and velocity field, pressure distribution, and the temperature variation across the sample region inside an environmental transmission electron microscope (ETEM) have been modeled by means of computational fluid dynamics (CFD). Heating the sample area by a furnace type TEM holder...... gives rise to temperature gradients over the sample area. Three major mechanisms have been identified with respect to heat transfer in the sample area: radiation from the grid, conduction in the grid, and conduction in the gas. A parameter sensitivity analysis showed that the sample temperature...... was affected by the conductivity of the gas, the emissivity of the sample grid, and the conductivity of the grid. Ideally the grid should be polished and made from a material with good conductivity, e.g. copper. With hydrogen gas, which has the highest conductivity of the gases studied, the temperature...
Ellis, Alicia M.; Garcia, Andres J.; Focks, Dana A.; Morrison, Amy C.; Scott, Thomas W.
2011-01-01
Models can be useful tools for understanding the dynamics and control of mosquito-borne disease. More detailed models may be more realistic and better suited for understanding local disease dynamics; however, evaluating model suitability, accuracy, and performance becomes increasingly difficult with greater model complexity. Sensitivity analysis is a technique that permits exploration of complex models by evaluating the sensitivity of the model to changes in parameters. Here, we present results of sensitivity analyses of two interrelated complex simulation models of mosquito population dynamics and dengue transmission. We found that dengue transmission may be influenced most by survival in each life stage of the mosquito, mosquito biting behavior, and duration of the infectious period in humans. The importance of these biological processes for vector-borne disease models and the overwhelming lack of knowledge about them make acquisition of relevant field data on these biological processes a top research priority. PMID:21813844
A probabilistic transmission and population dynamic model to assess tuberculosis infection risk.
Liao, Chung-Min; Cheng, Yi-Hsien; Lin, Yi-Jun; Hsieh, Nan-Hung; Huang, Tang-Luen; Chio, Chia-Pin; Chen, Szu-Chieh; Ling, Min-Pei
2012-08-01
The purpose of this study was to examine tuberculosis (TB) population dynamics and to assess potential infection risk in Taiwan. A well-established mathematical model of TB transmission built on previous models was adopted to study the potential impact of TB transmission. A probabilistic risk model was also developed to estimate site-specific risks of developing disease soon after recent primary infection, exogenous reinfection, or through endogenous reactivation (latently infected TB) among Taiwan regions. Here, we showed that the proportion of endogenous reactivation (53-67%) was larger than that of exogenous reinfection (32-47%). Our simulations showed that as epidemic reaches a steady state, age distribution of cases would finally shift toward older age groups dominated by latently infected TB cases as a result of endogenous reactivation. A comparison of age-weighted TB incidence data with our model simulation output with 95% credible intervals revealed that the predictions were in an apparent agreement with observed data. The median value of overall basic reproduction number (R₀) in eastern Taiwan ranged from 1.65 to 1.72, whereas northern Taiwan had the lowest R₀ estimate of 1.50. We found that total TB incidences in eastern Taiwan had 25-27% probabilities of total proportion of infected population exceeding 90%, whereas there were 36-66% probabilities having exceeded 20% of total proportion of infected population attributed to latently infected TB. We suggested that our Taiwan-based analysis can be extended to the context of developing countries, where TB remains a substantial cause of elderly morbidity and mortality. © 2012 Society for Risk Analysis.
Two time-delay dynamic model on the transmission of malicious signals in wireless sensor network
International Nuclear Information System (INIS)
Keshri, Neha; Mishra, Bimal Kumar
2014-01-01
Highlights: • Role of time delay to reduce the adversary effect in WSN is explored. • Model with two time delays is proposed to analyse spread of malicious signal in WSN. • Dynamical behaviour of worm-free equilibrium and endemic equilibrium is shown. • Threshold condition for switch of stability are obtained analytically. • Relation between stability and the two time delays is also explored. - Abstract: Deployed in a hostile environment, motes of a Wireless sensor network (WSN) could be easily compromised by the attackers because of several constraints such as limited processing capabilities, memory space, and limited battery life time etc. While transmitting the data to their neighbour motes within the network, motes are easily compromised due to resource constraints. Here time delay can play an efficient role to reduce the adversary effect on motes. In this paper, we propose an epidemic model SEIR (Susceptible–Exposed–Infectious–Recovered) with two time delays to describe the transmission dynamics of malicious signals in wireless sensor network. The first delay accounts for an exposed (latent) period while the second delay is for the temporary immunity period due to multiple worm outbreaks. The dynamical behaviour of worm-free equilibrium and endemic equilibrium is shown from the point of stability which switches under some threshold condition specified by the basic reproduction number. Our results show that the global properties of equilibria also depends on the threshold condition and that latent and temporary immunity period in a mote does not affect the stability, but they play a positive role to control malicious attack. Moreover, numerical simulations are given to support the theoretical analysis
International Nuclear Information System (INIS)
Mølgaard Mortensen, Peter; Willum Hansen, Thomas; Birkedal Wagner, Jakob; Degn Jensen, Anker
2015-01-01
The temperature and velocity field, pressure distribution, and the temperature variation across the sample region inside an environmental transmission electron microscope (ETEM) have been modeled by means of computational fluid dynamics (CFD). Heating the sample area by a furnace type TEM holder gives rise to temperature gradients over the sample area. Three major mechanisms have been identified with respect to heat transfer in the sample area: radiation from the grid, conduction in the grid, and conduction in the gas. A parameter sensitivity analysis showed that the sample temperature was affected by the conductivity of the gas, the emissivity of the sample grid, and the conductivity of the grid. Ideally the grid should be polished and made from a material with good conductivity, e.g. copper. With hydrogen gas, which has the highest conductivity of the gases studied, the temperature difference over the TEM grid is less than 5 °C, at what must be considered typical conditions, and it is concluded that the conditions on the sample grid in the ETEM can be considered as isothermal during general use. - Highlights: • Computational fluid dynamics used for mapping flow and temperature in ETEM setup. • Temperature gradient across TEM grid in furnace based heating holder very small in ETEM. • Conduction from TEM grid and gas in addition to radiation from TEM grid most important. • Pressure drop in ETEM limited to the pressure limiting apertures
Dynamically prioritized progressive transmission
Blanford, Ronald
1992-04-01
Retrieval of image data from a centralized database may be subject to bandwidth limitations, whether due to a low-bandwidth communications link or to contention from simultaneous accesses over a high-bandwidth link. Progressive transmission can alleviate this problem by encoding image data so that any prefix of the data stream approximates the complete image at a coarse level of resolution. The longer the prefix, the finer the resolution. In many cases, as little at 1 percent of the image data may be sufficient to decide whether to discard the image, to permit the retrieval to continue, or to restrict retrieval to a subsection of the image. Our approach treats resolution not as a fixed attribute of the image, but rather as a resource which may be allocated to portions of the image at the direction of a user-specified priority function. The default priority function minimizes error by allocating more resolution to regions of high variance. The user may also point to regions of interest requesting priority transmission. More advanced target recognition strategies may be incorporated at the user's discretion. Multispectral imagery is supported. The user engineering implications are profounded. There is immediate response to a query that might otherwise take minutes to complete. The data is transmitted in small increments so that no single user dominates the communications bandwidth. The user-directed improvement means that bandwidth is focused on interesting information. The user may continue working with the first coarse approximations while further image data is still arriving. The algorithm has been implemented in C on Sun, Silicon Graphics, and NeXT workstations, and in Lisp on a Symbolics. Transmission speeds reach as high as 60,000 baud using a Sparc or 68040 processor when storing data to memory; somewhat less if also updating a graphical display. The memory requirements are roughly five bytes per image pixel. Both computational and memory costs may be reduced
Dynamics of synthetic drugs transmission model with psychological addicts and general incidence rate
Ma, Mingju; Liu, Sanyang; Xiang, Hong; Li, Jun
2018-02-01
Synthetic drugs are replacing traditional ones and becoming the main popular ones gradually, which have given rise to serious social issues in recent years. In this paper, a synthetic drugs transmission model with psychological addicts and general contact rate is proposed. The local and global stabilities are decided by the basic reproduction number R0. By analyzing the sensitivity of parameters, we obtain that controlling psychological addiction is better than drugs treatment. These results are verified by numerical simulations.
Dynamical Behavior of a Rumor Transmission Model with Psychological Effect in Emergency Event
Directory of Open Access Journals (Sweden)
Liang'an Huo
2013-01-01
Full Text Available A rumor transmission model with nonmonotonic incidence rate was proposed, which provides excellent explanations of the “psychological” effect with rumor spreading in emergency event. By carrying out a global analysis of the model and studying the stability of the rumor-free equilibrium and the rumor-endemic equilibrium, we showed that either the number of infective individuals tends to zero as time evolves or the rumor persists. Finally, recommendations for policy makers and consulting advice for related commissions are explored in the case study of crazy rumors propagated for the iodized sail shortage panic in China.
Pitman, Richard; Fisman, David; Zaric, Gregory S.; Postma, Maarten; Kretzschmar, Mirjam; Edmunds, John; Brisson, Marc
2012-01-01
The transmissible nature of communicable diseases is what sets them apart from other diseases modeled by health economists. The probability of a susceptible individual becoming infected at any one point in time (the force of infection) is related to the number of infectious individuals in the
Pitman, Richard; Fisman, David; Zaric, Gregory S.; Postma, Maarten; Kretzschmar, Mirjam; Edmunds, John; Brisson, Marc
2012-01-01
The transmissible nature of communicable diseases is what sets them apart from other diseases modeled by health economists. The probability of a susceptible individual becoming infected at any one point in time (the force of infection) is related to the number of infectious individuals in the
Lewnard, Joseph A.; Ndeffo Mbah, Martial L.; Alfaro-Murillo, Jorge A.; Altice, Frederick L.; Bawo, Luke; Nyenswah, Tolbert G.; Galvani, Alison P.
2014-01-01
Background A substantial scale-up in public health response is needed to control the unprecedented Ebola virus disease (EVD) epidemic in West Africa. Current international commitments seek to expand intervention capacity in three areas: new EVD Treatment Centers (ETCs); case ascertainment through contact tracing; and household protective kit allocation. Methods We developed a transmission model of Ebola virus that we fitted to reported EVD cases and deaths in Montserrado County, Liberia. We used this model to evaluate effectiveness of expanding ETCs, improving case ascertainment, and allocating protective kits for controlling the outbreak in Montserrado. Findings We estimated the basic reproductive number for EVD in Montserrado to be 2·49 [2·38–2·60]. We expect that allocating 4,800 additional ETC beds and increasing case ascertainment fivefold in November can avert 77312 [68400–85870] cases relative to the status quo by 15 December. Complementing these measures with protective kit allocation increases the expectation as high as 97940 [90096–105606] cases. If deployed by 15 October, equivalent interventions would have been expected to avert 137432 [129736–145874] cases. If delayed to 15 November, we expect the interventions will at best avert 53957 [49963–60490] cases. Interpretation The number of ETC beds needed to effectively control EVD in Montserrado substantially exceeds the total pledged by the United States to West Africa. Accelerated case ascertainment is required to maximize effectiveness of expanding ETC capacity. Distributing protective kits can further augment EVD prevention. Our findings highlight the rapidly closing window of opportunity for controlling the outbreak and averting a catastrophic toll of EVD cases and deaths. Funding NIH: U01-GM087719, U01-GM105627, K24-DA017072 PMID:25455986
Goff, P.; Hulse, A.; Harder, H. R.; Pierce, L. A.; Rizzo, D.; Hanley, J.; Orantes, L.; Stevens, L.; Justi, S.; Monroy, C.
2015-12-01
A computational simulation has been designed as an investigative case study by high school students to introduce system dynamics modeling into high school curriculum. This case study approach leads users through the forensics necessary to diagnose an unknown disease in a Central American village. This disease, Chagas, is endemic to 21 Latin American countries. The CDC estimates that of the 110 million people living in areas with the disease, 8 million are infected, with as many as 300,000 US cases. Chagas is caused by the protozoan parasite, Trypanosoma cruzi, and is spread via blood feeding insect (vectors), that feed on vertebrates and live in crevasses in the walls and roofs of adobe homes. One-third of the infected people will develop chronic Chagas who are asymptomatic for years before their heart or GI tract become enlarged resulting in death. The case study has three parts. Students play the role of WHO field investigators and work collaboratively to: 1) use genetics to identify the host(s) and vector of the disease 2) use a STELLA™ SIR (Susceptible, Infected, Recovered) system dynamics model to study Chagas at the village scale and 3) develop management strategies. The simulations identify mitigation strategies known as Ecohealth Interventions (e.g., home improvements using local materials) to help stakeholders test and compare multiple optima. High school students collaborated with researchers from the University of Vermont, Loyola University and Universidad de San Carlos, Guatemala, working in labs, interviewing researchers, and incorporating mulitple field data as part of a NSF-funded multiyear grant. The model displays stable equilibria of hosts, vectors, and disease-states. Sensitivity analyses show measures of household condition and presence of vertebrates were significant leverage points, supporting other findings by the University research team. The village-scale model explores multiple solutions to disease mitigation for the purpose of producing
Boemer, J.C.; Gibescu, M.; Kling, W.L.
2009-01-01
Distributed Generation is increasing in nowadays power systems. Small scale systems such as photovoltaic, biomass or small cogeneration plants are connected to the distribution level, while large wind farms will be connected to the transmission level. Both trends lead to a replacement of large
International Nuclear Information System (INIS)
Xu Donghua; Wirth, Brian D.; Li Meimei; Kirk, Marquis A.
2012-01-01
We present a combinatorial approach that integrates state-of-the-art transmission electron microscopy (TEM) in situ irradiation experiments and high-performance computing techniques to study irradiation defect dynamics in metals. Here, we have studied the evolution of visible defect clusters in nanometer-thick molybdenum foils under 1 MeV krypton ion irradiation at 80 °C through both cluster dynamics modeling and in situ TEM experiments. The experimental details are reported elsewhere; we focus here on the details of model construction and comparing the model with the experiments. The model incorporates continuous production of point defects and/or small clusters, and the accompanying interactions, which include clustering, recombination and loss to the surfaces that result from the diffusion of the mobile defects. To account for the strong surface effect in thin TEM foils, the model includes one-dimensional spatial dependence along the foil depth, and explicitly treats the surfaces as black sinks. The rich amount of data (cluster number density and size distribution at a variety of foil thickness, irradiation dose and dose rate) offered by the advanced in situ experiments has allowed close comparisons with computer modeling and permitted significant validation and optimization of the model in terms of both physical model construct (damage production mode, identities of mobile defects) and parameterization (diffusivities of mobile defects). The optimized model exhibits good qualitative and quantitative agreement with the in situ TEM experiments. The combinatorial approach is expected to bring a unique opportunity for the study of radiation damage in structural materials.
DeSmidt, Hans A.; Smith, Edward C.; Bill, Robert C.; Wang, Kon-Well
2013-01-01
This project develops comprehensive modeling and simulation tools for analysis of variable rotor speed helicopter propulsion system dynamics. The Comprehensive Variable-Speed Rotorcraft Propulsion Modeling (CVSRPM) tool developed in this research is used to investigate coupled rotor/engine/fuel control/gearbox/shaft/clutch/flight control system dynamic interactions for several variable rotor speed mission scenarios. In this investigation, a prototypical two-speed Dual-Clutch Transmission (DCT) is proposed and designed to achieve 50 percent rotor speed variation. The comprehensive modeling tool developed in this study is utilized to analyze the two-speed shift response of both a conventional single rotor helicopter and a tiltrotor drive system. In the tiltrotor system, both a Parallel Shift Control (PSC) strategy and a Sequential Shift Control (SSC) strategy for constant and variable forward speed mission profiles are analyzed. Under the PSC strategy, selecting clutch shift-rate results in a design tradeoff between transient engine surge margins and clutch frictional power dissipation. In the case of SSC, clutch power dissipation is drastically reduced in exchange for the necessity to disengage one engine at a time which requires a multi-DCT drive system topology. In addition to comprehensive simulations, several sections are dedicated to detailed analysis of driveline subsystem components under variable speed operation. In particular an aeroelastic simulation of a stiff in-plane rotor using nonlinear quasi-steady blade element theory was conducted to investigate variable speed rotor dynamics. It was found that 2/rev and 4/rev flap and lag vibrations were significant during resonance crossings with 4/rev lagwise loads being directly transferred into drive-system torque disturbances. To capture the clutch engagement dynamics, a nonlinear stick-slip clutch torque model is developed. Also, a transient gas-turbine engine model based on first principles mean
Directory of Open Access Journals (Sweden)
Adam J Kucharski
2016-05-01
Full Text Available Between October 2013 and April 2014, more than 30,000 cases of Zika virus (ZIKV disease were estimated to have attended healthcare facilities in French Polynesia. ZIKV has also been reported in Africa and Asia, and in 2015 the virus spread to South America and the Caribbean. Infection with ZIKV has been associated with neurological complications including Guillain-Barré Syndrome (GBS and microcephaly, which led the World Health Organization to declare a Public Health Emergency of International Concern in February 2015. To better understand the transmission dynamics of ZIKV, we used a mathematical model to examine the 2013-14 outbreak on the six major archipelagos of French Polynesia. Our median estimates for the basic reproduction number ranged from 2.6-4.8, with an estimated 11.5% (95% CI: 7.32-17.9% of total infections reported. As a result, we estimated that 94% (95% CI: 91-97% of the total population of the six archipelagos were infected during the outbreak. Based on the demography of French Polynesia, our results imply that if ZIKV infection provides complete protection against future infection, it would take 12-20 years before there are a sufficient number of susceptible individuals for ZIKV to re-emerge, which is on the same timescale as the circulation of dengue virus serotypes in the region. Our analysis suggests that ZIKV may exhibit similar dynamics to dengue virus in island populations, with transmission characterized by large, sporadic outbreaks with a high proportion of asymptomatic or unreported cases.
S.M. Moore; C.A. Manore; V.A. Bokil; E.T. Borer; P.R. Hosseini
2011-01-01
Many generalist pathogens are influenced by the spatial distributions and relative abundances of susceptible host species. The spatial structure of host populations can influence patterns of infection incidence (or disease outbreaks), and the effects of a generalist pathogen on host community dynamics in a spatially heterogeneous community may differ from predictions...
Pambour, Kwabena Addo; Cakir Erdener, Burcin; Bolado-Lavin, Ricardo; Dijkema, Gerhard P.J.
2017-01-01
The integration of renewable energy sources into existing electric power systems is connected with an increased interdependence between natural gas and electricity transmission networks. To analyse this interdependence and its impact on security of supply, we developed a novel quasi-dynamic
Modelling the effects of sexting on the transmission dynamics of HSV-2 amongst adolescents
Directory of Open Access Journals (Sweden)
A. Mhlanga
2015-12-01
Full Text Available Prior studies have indicated that adolescents who are into sexting are likely to engage in risky sexual behaviours. In this paper, a mathematical model to assess the impact of sexting and peer influence on the spread of HSV-2 amongst adolescents is developed. The threshold parameters of the model are determined and stabilities are analysed. The impact of filtering and awareness campaigns is explored. Results from the study suggest that HSV-2 prevalence is high amongst adolescents who are into sexting as compared to those who do not. Further, we applied optimal control theory to the proposed model. The controls represent filtering and awareness campaigns. The objective is based on minimising the susceptible sexting adolescents, infected non-sexting adolescents and the infected sexting adolescents. The optimal control is characterised and numerically solved. Overall, the application of optimal control theory suggests that more effort should be devoted to both controls, filtering and awareness campaigns.
DEFF Research Database (Denmark)
Olsen, Rasmus; Anders, George J.; Holboell, Joachim
2013-01-01
This paper presents an algorithm for the estimation of the time-dependent temperature evolution of power cables, when real-time temperature measurements of the cable surface or a point within its vicinity are available. The thermal resistivity and specific heat of the cable surroundings are varied...... as functions of the moisture content which is known to vary with time. Furthermore, issues related to the cooling effect during rainy weather are considered. The algorithm is based on the lumped parameters model and takes as input distributed temperature sensing measurements as well as the current and ambient...... temperature. The concept is verified by studying a laboratory setup of a 245 kV cable system....
Directory of Open Access Journals (Sweden)
Cristian ePasquaretta
2016-04-01
Full Text Available Social learning – the transmission of behaviors through observation or interaction with conspecifics – can be viewed as a decision-making process driven by interactions among individuals. Animal group structures change over time and interactions among individuals occur in particular orders that may be repeated following specific patterns, change in their nature, or disappear completely. Here we used a stochastic actor-oriented model built using the RSiena package in R to estimate individual behaviors and their changes through time, by analyzing the dynamic of the interaction network of the fruit fly Drosophila melanogaster during social learning experiments. In particular, we re-analyzed an experimental dataset where uninformed flies, left free to interact with informed ones, acquired and later used information about oviposition site choice obtained by social interactions. We estimated the degree to which the uninformed flies had successfully acquired the information carried by informed individuals using the proportion of eggs laid by uninformed flies on the medium their conspecifics had been trained to favor. Regardless of the degree of information acquisition measured in uninformed individuals, they always received and started interactions more frequently than informed ones did. However, information was efficiently transmitted (i.e. uninformed flies predominantly laid eggs on the same medium informed ones had learn to prefer only when the difference in contacts sent between the two fly types was small. Interestingly, we found that the degree of reciprocation, the tendency of individuals to form mutual connections between each other, strongly affected oviposition site choice in uninformed flies. This work highlights the great potential of RSiena and its utility in the studies of interaction networks among non-human animals.
Gopalakrishnan, Ravichandran C; Karunakaran, Manivannan
2014-01-01
Nowadays, quality of service (QoS) is very popular in various research areas like distributed systems, multimedia real-time applications and networking. The requirements of these systems are to satisfy reliability, uptime, security constraints and throughput as well as application specific requirements. The real-time multimedia applications are commonly distributed over the network and meet various time constraints across networks without creating any intervention over control flows. In particular, video compressors make variable bit-rate streams that mismatch the constant-bit-rate channels typically provided by classical real-time protocols, severely reducing the efficiency of network utilization. Thus, it is necessary to enlarge the communication bandwidth to transfer the compressed multimedia streams using Flexible Time Triggered- Enhanced Switched Ethernet (FTT-ESE) protocol. FTT-ESE provides automation to calculate the compression level and change the bandwidth of the stream. This paper focuses on low-latency multimedia transmission over Ethernet with dynamic quality-of-service (QoS) management. This proposed framework deals with a dynamic QoS for multimedia transmission over Ethernet with FTT-ESE protocol. This paper also presents distinct QoS metrics based both on the image quality and network features. Some experiments with recorded and live video streams show the advantages of the proposed framework. To validate the solution we have designed and implemented a simulator based on the Matlab/Simulink, which is a tool to evaluate different network architecture using Simulink blocks.
Huang, Xiaodong; Clements, Archie C A; Williams, Gail; Mengersen, Kerrie; Tong, Shilu; Hu, Wenbiao
2016-04-01
A pandemic strain of influenza A spread rapidly around the world in 2009, now referred to as pandemic (H1N1) 2009. This study aimed to examine the spatiotemporal variation in the transmission rate of pandemic (H1N1) 2009 associated with changes in local socio-environmental conditions from May 7-December 31, 2009, at a postal area level in Queensland, Australia. We used the data on laboratory-confirmed H1N1 cases to examine the spatiotemporal dynamics of transmission using a flexible Bayesian, space-time, Susceptible-Infected-Recovered (SIR) modelling approach. The model incorporated parameters describing spatiotemporal variation in H1N1 infection and local socio-environmental factors. The weekly transmission rate of pandemic (H1N1) 2009 was negatively associated with the weekly area-mean maximum temperature at a lag of 1 week (LMXT) (posterior mean: -0.341; 95% credible interval (CI): -0.370--0.311) and the socio-economic index for area (SEIFA) (posterior mean: -0.003; 95% CI: -0.004--0.001), and was positively associated with the product of LMXT and the weekly area-mean vapour pressure at a lag of 1 week (LVAP) (posterior mean: 0.008; 95% CI: 0.007-0.009). There was substantial spatiotemporal variation in transmission rate of pandemic (H1N1) 2009 across Queensland over the epidemic period. High random effects of estimated transmission rates were apparent in remote areas and some postal areas with higher proportion of indigenous populations and smaller overall populations. Local SEIFA and local atmospheric conditions were associated with the transmission rate of pandemic (H1N1) 2009. The more populated regions displayed consistent and synchronized epidemics with low average transmission rates. The less populated regions had high average transmission rates with more variations during the H1N1 epidemic period. Copyright © 2016 Elsevier Inc. All rights reserved.
Huo, Liang'an; Jiang, Jiehui; Gong, Sixing; He, Bing
2016-05-01
Rumor transmission has become an important issue in emergency event. In this paper, a rumor transmission model with Holling-type II functional response was proposed, which provides excellent explanations of the scientific knowledge effect with rumor spreading. By a global analysis of the model and studying the stability of the rumor-free equilibrium and the rumor-endemic equilibrium, we found that the number of infective individuals equal to zero or positive integer as time went on. A numerical simulation is carried out to illustrate the feasibility of our main results. The results will provide the theoretical support to rumor control in emergency event and also provide decision makers references for the public opinions management.
Avian Influenza spread and transmission dynamics
Bourouiba, Lydia; Gourley, Stephen A.; Liu, Rongsong; Takekawa, John Y.; Wu, Jianhong; Chen, Dongmei; Moulin, Bernard; Wu, Jianhong
2015-01-01
The spread of highly pathogenic avian influenza (HPAI) viruses of type A of subtype H5N1 has been a serious threat to global public health. Understanding the roles of various (migratory, wild, poultry) bird species in the transmission of these viruses is critical for designing and implementing effective control and intervention measures. Developing appropriate models and mathematical techniques to understand these roles and to evaluate the effectiveness of mitigation strategies have been a challenge. Recent development of the global health surveillance (especially satellite tracking and GIS techniques) and the mathematical theory of dynamical systems combined have gradually shown the promise of some cutting-edge methodologies and techniques in mathematical biology to meet this challenge.
Analysis on Dynamic Transmission Accuracy for RV Reducer
Directory of Open Access Journals (Sweden)
Zhang Fengshou
2017-01-01
Full Text Available By taking rotate vector (RV reducer as the research object, the factors affecting the transmission accuracy are studied, including the machining errors of the main parts, assembly errors, clearance, micro-displacement, gear mesh stiffness and damping, bearing stiffness. Based on Newton second law, the transmission error mathematical model of RV reducer is set up. Then, the RV reducer transmission error curve is achieved by solving the mathematical model using the Runge-Kutta methods under the combined action of various error factors. Through the analysis of RV reducer transmission test, it can be found that there are similar variation trend and frequency components compared the theoretical research and experimental result. The presented method is useful to the research on dynamic transmission accuracy of RV reducer, and also applies to research the transmission accuracy of other cycloid drive systems.
The dynamics of transmission and the dynamics of networks.
Farine, Damien
2017-05-01
A toy example depicted here highlighting the results of a study in this issue of the Journal of Animal Ecology that investigates the impact of network dynamics on potential disease outbreaks. Infections (stars) that spread by contact only (left) reduce the predicted outbreak size compared to situations where individuals can become infected by moving through areas that previously contained infected individuals (right). This is potentially important in species where individuals, or in this case groups, have overlapping ranges (as depicted on the top right). Incorporating network dynamics that maintain information about the ordering of contacts (central blocks; including the ordering of spatial overlap as noted by the arrows that highlight the blue group arriving after the red group in top-right of the figure) is important for capturing how a disease might not have the opportunity to spread to all individuals. By contrast, a static or 'average' network (lower blocks) does not capture any of these dynamics. Interestingly, although static networks generally predict larger outbreak sizes, the authors find that in cases when transmission probability is low, this prediction can switch as a result of changes in the estimated intensity of contacts among individuals. [Colour figure can be viewed at wileyonlinelibrary.com]. Springer, A., Kappeler, P.M. & Nunn, C.L. (2017) Dynamic vs. static social networks in models of parasite transmission: Predicting Cryptosporidium spread in wild lemurs. Journal of Animal Ecology, 86, 419-433. The spread of disease or information through networks can be affected by several factors. Whether and how these factors are accounted for can fundamentally change the predicted impact of a spreading epidemic. Springer, Kappeler & Nunn () investigate the role of different modes of transmission and network dynamics on the predicted size of a disease outbreak across several groups of Verreaux's sifakas, a group-living species of lemur. While some factors
DEFF Research Database (Denmark)
Woolsey, Ian David; Bune, Nethe Eva Touborg; Jensen, Per Moestrup
2015-01-01
We propose a model involving the oral inoculation of Echinococcus multilocularis eggs in a vole species and examine the infection dynamics in a dose-response experiment. Defined doses, 100 (n = 8), 500 (n = 5) and 1000 (n = 5) of E. multilocularis eggs were used to inoculate Microtus agrestis. Four...
Dynamics of a split torque helicopter transmission
Krantz, Timothy L.
1994-06-01
Split torque designs, proposed as alternatives to traditional planetary designs for helicopter main rotor transmissions, can save weight and be more reliable than traditional designs. This report presents the results of an analytical study of the system dynamics and performance of a split torque gearbox that uses a balance beam mechanism for load sharing. The Lagrange method was applied to develop a system of equations of motion. The mathematical model includes time-varying gear mesh stiffness, friction, and manufacturing errors. Cornell's method for calculating the stiffness of spur gear teeth was extended and applied to helical gears. The phenomenon of sidebands spaced at shaft frequencies about gear mesh fundamental frequencies was simulated by modeling total composite gear errors as sinusoid functions. Although the gearbox has symmetric geometry, the loads and motions of the two power paths differ. Friction must be considered to properly evaluate the balance beam mechanism. For the design studied, the balance beam is not an effective device for load sharing unless the coefficient of friction is less than 0.003. The complete system stiffness as represented by the stiffness matrix used in this analysis must be considered to precisely determine the optimal tooth indexing position.
Modeling seasonal measles transmission in China
Bai, Zhenguo; Liu, Dan
2015-08-01
A discrete-time deterministic measles model with periodic transmission rate is formulated and studied. The basic reproduction number R0 is defined and used as the threshold parameter in determining the dynamics of the model. It is shown that the disease will die out if R0 1 . Parameters in the model are estimated on the basis of demographic and epidemiological data. Numerical simulations are presented to describe the seasonal fluctuation of measles infection in China.
Dynamics of tuberculosis transmission with exogenous reinfections and endogenous reactivation
Khajanchi, Subhas; Das, Dhiraj Kumar; Kar, Tapan Kumar
2018-05-01
We propose and analyze a mathematical model for tuberculosis (TB) transmission to study the role of exogenous reinfection and endogenous reactivation. The model exhibits two equilibria: a disease free and an endemic equilibria. We observe that the TB model exhibits transcritical bifurcation when basic reproduction number R0 = 1. Our results demonstrate that the disease transmission rate β and exogenous reinfection rate α plays an important role to change the qualitative dynamics of TB. The disease transmission rate β give rises to the possibility of backward bifurcation for R0 < 1, and hence the existence of multiple endemic equilibria one of which is stable and another one is unstable. Our analysis suggests that R0 < 1 may not be sufficient to completely eliminate the disease. We also investigate that our TB transmission model undergoes Hopf-bifurcation with respect to the contact rate β and the exogenous reinfection rate α. We conducted some numerical simulations to support our analytical findings.
Transmission dynamic range in chest radiology
International Nuclear Information System (INIS)
Lemmers, H.E.A.S.J.; Schultze Kool, L.J.; van Elburg, H.J.; Boelens, F.
1989-01-01
Due to the large difference in transmission between the lung area and the mediastinum, the human chest is a challenging object for radiographic imaging. This study is performed in order to define the dynamic range needed for a chest imaging chain. Eight hundred seventy-five consecutive outpatients were imaged with a prototype AMBER (advanced multiple beam equalization radiography) unit at 141 kVp. The equalization facility was disabled, allowing for the simultaneous capture of a film image and a digital dataset representing the local patient transmission in fields of approximately 2x2 cm. The datasets were analyzed to obtain the relation between the average transmission distribution in a subset of the population and physical parameters characterizing this subset, such as body weight or length
Transmission probability-based dynamic power control for multi-radio mesh networks
CSIR Research Space (South Africa)
Olwal, TO
2008-09-01
Full Text Available This paper presents an analytical model for the selection of the transmission power based on the bi-directional medium access information. Most of dynamic transmission power control algorithms are based on the single directional channel...
Forecasting Ebola with a regression transmission model
Directory of Open Access Journals (Sweden)
Jason Asher
2018-03-01
Full Text Available We describe a relatively simple stochastic model of Ebola transmission that was used to produce forecasts with the lowest mean absolute error among Ebola Forecasting Challenge participants. The model enabled prediction of peak incidence, the timing of this peak, and final size of the outbreak. The underlying discrete-time compartmental model used a time-varying reproductive rate modeled as a multiplicative random walk driven by the number of infectious individuals. This structure generalizes traditional Susceptible-Infected-Recovered (SIR disease modeling approaches and allows for the flexible consideration of outbreaks with complex trajectories of disease dynamics. Keywords: Ebola, Forecasting, Mathematical modeling, Bayesian inference
Adisasmito, Wiku; Hunter, Benjamin M; Krumkamp, Ralf; Latief, Kamal; Rudge, James W; Hanvoravongchai, Piya; Coker, Richard J
2015-03-01
The failure to contain pandemic influenza A(H1N1) 2009 in Mexico has shifted global attention from containment to mitigation. Limited surveillance and reporting have, however, prevented detailed assessment of mitigation during the pandemic, particularly in low- and middle-income countries. To assess pandemic influenza case management capabilities in a resource-limited setting, the authors used a health system questionnaire and density-dependent, deterministic transmission model for Bali, Indonesia, determining resource gaps. The majority of health resources were focused in and around the provincial capital, Denpasar; however, gaps are found in every district for nursing staff, surgical masks, and N95 masks. A relatively low pathogenicity pandemic influenza virus would see an overall surplus for physicians, antivirals, and antimicrobials; however, a more pathogenic virus would lead to gaps in every resource except antimicrobials. Resources could be allocated more evenly across Bali. These, however, are in short supply universally and therefore redistribution would not fill resource gaps. © 2011 APJPH.
Biology as population dynamics: heuristics for transmission risk.
Keebler, Daniel; Walwyn, David; Welte, Alex
2013-02-01
Population-type models, accounting for phenomena such as population lifetimes, mixing patterns, recruitment patterns, genetic evolution and environmental conditions, can be usefully applied to the biology of HIV infection and viral replication. A simple dynamic model can explore the effect of a vaccine-like stimulus on the mortality and infectiousness, which formally looks like fertility, of invading virions; the mortality of freshly infected cells; and the availability of target cells, all of which impact on the probability of infection. Variations on this model could capture the importance of the timing and duration of different key events in viral transmission, and hence be applied to questions of mucosal immunology. The dynamical insights and assumptions of such models are compatible with the continuum of between- and within-individual risks in sexual violence and may be helpful in making sense of the sparse data available on the association between HIV transmission and sexual violence. © 2012 John Wiley & Sons A/S.
Yaesoubi, Reza; Trotter, Caroline; Colijn, Caroline; Yaesoubi, Maziar; Colombini, Anaïs; Resch, Stephen; Kristiansen, Paul A; LaForce, F Marc; Cohen, Ted
2018-01-01
The introduction of a conjugate vaccine for serogroup A Neisseria meningitidis has dramatically reduced disease in the African meningitis belt. In this context, important questions remain about the performance of different vaccine policies that target remaining serogroups. Here, we estimate the health impact and cost associated with several alternative vaccination policies in Burkina Faso. We developed and calibrated a mathematical model of meningococcal transmission to project the disability-adjusted life years (DALYs) averted and costs associated with the current Base policy (serogroup A conjugate vaccination at 9 months, as part of the Expanded Program on Immunization [EPI], plus district-specific reactive vaccination campaigns using polyvalent meningococcal polysaccharide [PMP] vaccine in response to outbreaks) and three alternative policies: (1) Base Prime: novel polyvalent meningococcal conjugate (PMC) vaccine replaces the serogroup A conjugate in EPI and is also used in reactive campaigns; (2) Prevention 1: PMC used in EPI and in a nationwide catch-up campaign for 1-18-year-olds; and (3) Prevention 2: Prevention 1, except the nationwide campaign includes individuals up to 29 years old. Over a 30-year simulation period, Prevention 2 would avert 78% of the meningococcal cases (95% prediction interval: 63%-90%) expected under the Base policy if serogroup A is not replaced by remaining serogroups after elimination, and would avert 87% (77%-93%) of meningococcal cases if complete strain replacement occurs. Compared to the Base policy and at the PMC vaccine price of US$4 per dose, strategies that use PMC vaccine (i.e., Base Prime and Preventions 1 and 2) are expected to be cost saving if strain replacement occurs, and would cost US$51 (-US$236, US$490), US$188 (-US$97, US$626), and US$246 (-US$53, US$703) per DALY averted, respectively, if strain replacement does not occur. An important potential limitation of our study is the simplifying assumption that all
Zika virus transmission dynamic model and its optimal control%Zika病毒传播动力学模型及其最优控制
Institute of Scientific and Technical Information of China (English)
丁春晓; 朱元国
2016-01-01
In order to investigate the transimission law of Zika virus, we construct a Zika virus transmission dynamics model with Logistic growth rate. The existence of the disease free equilibrium and endemic equilibrium of the model are proved. The basic reproduction number is calculated to demonstrate the threshold of the disease outbreak. Based on the model,we present the corresponding optimal control problem,propose the necessary condition for the existence of the solution,and obtain the optimal solution. Finally, numerical simulations of different control strategies give the effectiveness of the model and the rationality of control strategies.%为了探究Zika病毒传播规律，创建了具有Logistic增长率的Zika病毒传播动力学模型。证明了模型无病平衡点和地方病平衡点的存在性，计算了疾病爆发阈值———基本再生数。随后，提出了基于模型的最优控制问题，给出了最优解存在的必要条件并求得了最优解。最后通过数值仿真例子，对比不同控制策略，证明了模型的有效性和控制策略的合理性。
Bilcke, Joke; Chapman, Ruth; Atchison, Christina; Cromer, Deborah; Johnson, Helen; Willem, Lander; Cox, Martin; Edmunds, William John; Jit, Mark
2015-07-01
Two vaccines (Rotarix and RotaTeq) are highly effective at preventing severe rotavirus disease. Rotavirus vaccination has been introduced in the United Kingdom and other countries partly based on modeling and cost-effectiveness results. However, most of these models fail to account for the uncertainty about several vaccine characteristics and the mechanism of vaccine action. A deterministic dynamic transmission model of rotavirus vaccination in the United Kingdom was developed. This improves on previous models by 1) allowing for 2 different mechanisms of action for Rotarix and RotaTeq, 2) using clinical trial data to understand these mechanisms, and 3) accounting for uncertainty by using Markov Chain Monte Carlo. In the long run, Rotarix and RotaTeq are predicted to reduce the overall rotavirus incidence by 50% (39%-63%) and 44% (30%-62%), respectively but with an increase in incidence in primary school children and adults up to 25 y of age. The vaccines are estimated to give more protection than 1 or 2 natural infections. The duration of protection is highly uncertain but has only impact on the predicted reduction in rotavirus burden for values lower than 10 y. The 2 vaccine mechanism structures fit equally well with the clinical trial data. Long-term postvaccination dynamics cannot be predicted reliably with the data available. Accounting for the joint uncertainty of several vaccine characteristics resulted in more insight into which of these are crucial for determining the impact of rotavirus vaccination. Data for up to at least 10 y postvaccination and covering older children and adults are crucial to address remaining questions on the impact of widespread rotavirus vaccination. © The Author(s) 2015.
Varicella susceptibility and transmission dynamics in Slovenia
Directory of Open Access Journals (Sweden)
Berginc Nataša
2010-06-01
Full Text Available Abstract Background A cross-sectional, age-stratified study was conducted to determine varicella-zoster seroprevalence and force of infection in Slovenia. Methods 3689 serum samples were tested for VZV IgG antibodies with an enzyme immunoassay. Semiparametric and parametric modelling were used to estimate the force of infection. Results Overall, 85.6% of serum samples were seropositive. Age-specific prevalence rose rapidly in preschool children and over 90% of 8 years old tested positive for VZV. However, 2.8% of serum samples among women of childbearing age were seronegative. Semiparametric modelling yielded force of infection estimates of 0.182 (95% CI 0.158-0.206, 0.367 (95% CI 0.285-0.448 and 0.008 (95% CI 0.0-0.032 for age groups 0.5- Conclusions Regardless of the age grouping used, the highest transmission occurred in children in their first years of school.
Directory of Open Access Journals (Sweden)
Kawai Kosuke
2012-10-01
Full Text Available Abstract Background Cervical cancer is the second most common cancer among women in Brazil. We examined the health and economic impacts of quadrivalent HPV vaccination in Brazil. Methods We adapted a previously developed transmission dynamic model to estimate the effectiveness of HPV vaccination on cervical cancer, cervical intraepithelial neoplasia grades 2 and 3 (CIN2/3, CIN1, and genital warts. We evaluated following vaccination strategies: routine vaccination of 12-year-old girls and routine vaccination in combination with a catch-up vaccination of 12 to 26-year-old women. Results The model projected that the vaccination would reduce the incidence rates of HPV 6/11/16/18-related cervical cancer, CIN2/3, CIN1, and female genital warts by 94% to 98% at year 100. Routine vaccination in combination with a catch-up vaccination could prevent approximately 163,000 cases of cervical cancer, 48,000 deaths from cervical cancer, 2.3 million cases of CIN2/3, and 11.4 million genital warts in the next 50 years. The incremental cost-effectiveness ratios for female vaccination strategies ranged from R$350 to R$720 (US$219 to US$450 per quality-adjusted life year (QALY gained. Conclusions Our study demonstrates that quadrivalent HPV female vaccination can be a cost-effective public health intervention that can substantially reduce the burden of cervical diseases and genital warts in Brazil.
Transmission dynamics of two dengue serotypes with vaccination scenarios.
González Morales, N L; Núñez-López, M; Ramos-Castañeda, J; Velasco-Hernández, J X
2017-05-01
In this work we present a mathematical model that incorporates two Dengue serotypes. The model has been constructed to study both the epidemiological trends of the disease and conditions that allow coexistence in competing strains under vaccination. We consider two viral strains and temporary cross-immunity with one vector mosquito population. Results suggest that vaccination scenarios will not only reduce disease incidence but will also modify the transmission dynamics. Indeed, vaccination and cross immunity period are seen to decrease the frequency and magnitude of outbreaks but in a differentiated manner with specific effects depending upon the interaction vaccine and strain type. Copyright © 2016 Elsevier Inc. All rights reserved.
Gerlier, L; Lamotte, M; Grenèche, S; Lenne, X; Carrat, F; Weil-Olivier, C; Damm, O; Schwehm, M; Eichner, M
2017-04-01
We estimated the epidemiological and economic impact of extending the French influenza vaccination programme from at-risk/elderly (≥65 years) only to healthy children (2-17 years). A deterministic, age-structured, dynamic transmission model was used to simulate the transmission of influenza in the French population, using the current vaccination coverage with trivalent inactivated vaccine (TIV) in at-risk/elderly individuals (current strategy) or gradually extending the vaccination to healthy children (aged 2-17 years) with intranasal, quadrivalent live-attenuated influenza vaccine (QLAIV) from current uptake up to 50% (evaluated strategy). Epidemiological, medical resource use and cost data were taken from international literature and country-specific information. The model was calibrated to the observed numbers of influenza-like illness visits/year. The 10-year number of symptomatic cases of confirmed influenza and direct medical costs ('all-payer') were calculated for the 0-17- (direct and indirect effects) and ≥18-year-old (indirect effect). The incremental cost-effectiveness ratio (ICER) was calculated for the total population, using a 4% discount rate/year. Assuming 2.3 million visits/year and 1960 deaths/year, the model calibration yielded an all-year average basic reproduction number (R 0 ) of 1.27. In the population aged 0-17 years, QLAIV prevented 865,000 influenza cases/year (58.4%), preventing 10-year direct medical expenses of €374 million. In those aged ≥18 years with unchanged TIV coverage, 1.2 million cases/year were averted (27.6%) via indirect effects (additionally prevented expenses, €457 million). On average, 613 influenza-related deaths were averted annually overall. The ICER was €18,001/life-year gained. The evaluated strategy had a 98% probability of being cost-effective at a €31,000/life-year gained threshold. The model demonstrated strong direct and indirect benefits of protecting healthy children against influenza with
Matrix of transmission in structural dynamics
International Nuclear Information System (INIS)
Mukherjee, S.
1975-01-01
Within the last few years numerous papers have been published on the subject of matrix method in elasto-mechanics. 'Matrix of Transmission' is one of the methods in this field which has gained considerable attention in recent years. The basic philosophy adopted in this method is based on the idea of breaking up a complicated system into component parts with simple elastic and dynamic properties which can be readily expressed in matrix form. These component matrices are considered as building blocks, which are fitted together according to a set of predetermined rules which then provide the static and dynamic properties of the entire system. A common type of system occuring in engineering practice consists of a number of elements linked together end to end in the form of a chain. The 'Transfer Matrix' is ideally suited for such a system, because only successive multiplication is necessary to connect these elements together. The number of degrees of freedom and intermediate conditions present no difficulty. Although the 'Transfer Matrix' method is suitable for the treatment of branched and coupled systems its application to systems which do not have predominant chain topology is not effective. Apart from the requirement that the system be linearely elastic, no other restrictions are made. In this paper, it is intended to give a general outline and theoretical formulation of 'Transfer Matrix' and then its application to actual problems in structural dynamics related to seismic analysis. The natural frequencies of a freely vibrating elastic system can be found by applying proper end conditions. The end conditions will yield the frequency determinate to zero. By using a suitable numerical method, the natural frequencies and mode shapes are determined by making a frequency sweep within the range of interest. Results of an analysis of a typical nuclear building by this method show very close agreement with the results obtained by using ASKA and SAP IV program. Therefore
Wen, Yu-Wen; Wu, Hsin; Chang, Chee-Jen
2015-05-01
Vaccination can reduce the incidence and mortality of an infectious disease and thus increase the years of life and productivity for the entire society. But when determining the vaccination coverage rate, its economic burden is usually not taken into account. This article aimed to use a dynamic transmission modeling (DTM), which is based on a susceptible-infectious-recovered model and is a system of differential equations, to find the optimal vaccination coverage rate based on the economic burden of an infectious disease. Vaccination for pneumococcal diseases was used as an example to demonstrate the main purpose. 23-Valent pneumococcal polysaccharide vaccines (PPV23) and 13-valent pneumococcal conjugate vaccines (PCV13) have shown their cost-effectiveness in elderly and children, respectively. Scenarios analysis of PPV23 to elderly aged 65+ years and of PCV13 to children aged 0 to 4 years was applied to assess the optimal vaccination coverage rate based on the 5-year economic burden. Model parameters were derived from Taiwan's National Health Insurance Research Database, government data, and published literature. Various vaccination coverage rates, the vaccine efficacy, and all epidemiologic parameters were substituted into DTM, and all differential equations were solved in R Statistical Software. If the coverage rate of PPV23 for the elderly and of PCV13 for the children both reach 50%, the economic burden due to pneumococcal disease will be acceptable. This article provided an alternative perspective from the economic burden of diseases to obtain a vaccination coverage rate using the DTM. This will provide valuable information for vaccination policy decision makers. Copyright © 2015 International Society for Pharmacoeconomics and Outcomes Research (ISPOR). Published by Elsevier Inc. All rights reserved.
Shafie, Asrul Akmal; Yeo, Hui Yee; Coudeville, Laurent; Steinberg, Lucas; Gill, Balvinder Singh; Jahis, Rohani; Amar-Singh Hss
2017-05-01
Dengue disease poses a great economic burden in Malaysia. This study evaluated the cost effectiveness and impact of dengue vaccination in Malaysia from both provider and societal perspectives using a dynamic transmission mathematical model. The model incorporated sensitivity analyses, Malaysia-specific data, evidence from recent phase III studies and pooled efficacy and long-term safety data to refine the estimates from previous published studies. Unit costs were valued in $US, year 2013 values. Six vaccination programmes employing a three-dose schedule were identified as the most likely programmes to be implemented. In all programmes, vaccination produced positive benefits expressed as reductions in dengue cases, dengue-related deaths, life-years lost, disability-adjusted life-years and dengue treatment costs. Instead of incremental cost-effectiveness ratios (ICERs), we evaluated the cost effectiveness of the programmes by calculating the threshold prices for a highly cost-effective strategy [ICER price of $US32.39 for programme 6 (highly cost effective up to $US14.15) and up to a price of $US100.59 for programme 1 (highly cost effective up to $US47.96) from the provider perspective. The cost-effectiveness analysis is sensitive to under-reporting, vaccine protection duration and model time horizon. Routine vaccination for a population aged 13 years with a catch-up cohort aged 14-30 years in targeted hotspot areas appears to be the best-value strategy among those investigated. Dengue vaccination is a potentially good investment if the purchaser can negotiate a price at or below the cost-effective threshold price.
Garchitorena, Andrés; Ngonghala, Calistus N.; Texier, Gaëtan; Landier, Jordi; Eyangoh, Sara; Bonds, Matthew H.; Guégan, Jean-François; Roche, Benjamin
2015-12-01
Buruli Ulcer is a devastating skin disease caused by the pathogen Mycobacterium ulcerans. Emergence and distribution of Buruli ulcer cases is clearly linked to aquatic ecosystems, but the specific route of transmission of M. ulcerans to humans remains unclear. Relying on the most detailed field data in space and time on M. ulcerans and Buruli ulcer available today, we assess the relative contribution of two potential transmission routes -environmental and water bug transmission- to the dynamics of Buruli ulcer in two endemic regions of Cameroon. The temporal dynamics of Buruli ulcer incidence are explained by estimating rates of different routes of transmission in mathematical models. Independently, we also estimate statistical models of the different transmission pathways on the spatial distribution of Buruli ulcer. The results of these two independent approaches are corroborative and suggest that environmental transmission pathways explain the temporal and spatial patterns of Buruli ulcer in our endemic areas better than the water bug transmission.
Orlofske, Sarah A; Flaxman, Samuel M; Joseph, Maxwell B; Fenton, Andy; Melbourne, Brett A; Johnson, Pieter T J
2018-05-01
Understanding pathogen transmission is crucial for predicting and managing disease. Nonetheless, experimental comparisons of alternative functional forms of transmission remain rare, and those experiments that are conducted are often not designed to test the full range of possible forms. To differentiate among 10 candidate transmission functions, we used a novel experimental design in which we independently varied four factors-duration of exposure, numbers of parasites, numbers of hosts and parasite density-in laboratory infection experiments. We used interactions between amphibian hosts and trematode parasites as a model system and all candidate models incorporated parasite depletion. An additional manipulation involving anaesthesia addressed the effects of host behaviour on transmission form. Across all experiments, nonlinear transmission forms involving either a power law or a negative binomial function were the best-fitting models and consistently outperformed the linear density-dependent and density-independent functions. By testing previously published data for two other host-macroparasite systems, we also found support for the same nonlinear transmission forms. Although manipulations of parasite density are common in transmission studies, the comprehensive set of variables tested in our experiments revealed that variation in density alone was least likely to differentiate among competing transmission functions. Across host-pathogen systems, nonlinear functions may often more accurately represent transmission dynamics and thus provide more realistic predictions for infection. © 2017 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.
Transmission dynamics and resistance in staphylococci
Hetem, D.J.
2015-01-01
This thesis will focus on nosocomial transmission and resistance of S. aureus and CoNS. After the general introduction on S. aureus and coagulase-negative staphylococci, part II focuses on the nosocomial transmission capacity of different MRSA clones in the hospital setting. In chapter 2 the
Influence of Shaft Torsional Stiffness on Dynamic Response of Four-Stage Main Transmission System
Directory of Open Access Journals (Sweden)
Yuan Chen
2018-01-01
Full Text Available Dynamic response analysis has potential for increasing fatigue life of the components in the transmission of a multistage main transmission system. The calculated data can demonstrate the influence of shaft torsional stiffness on dynamic characteristics of the system. Detecting key shafts of the system and analyzing their sensitivity are important for the design of four-stage helicopter gear box. Lumped mass method is applied for dynamic modeling and Fourier method is used to solve differential equation of the system. Results of the analysis indicate that key shafts can be designed carefully to improve the performance of the transmission system.
Brisson, Marc; Bénard, Élodie; Drolet, Mélanie; Bogaards, Johannes A; Baussano, Iacopo; Vänskä, Simopekka; Jit, Mark; Boily, Marie-Claude; Smith, Megan A; Berkhof, Johannes; Canfell, Karen; Chesson, Harrell W; Burger, Emily A; Choi, Yoon H; De Blasio, Birgitte Freiesleben; De Vlas, Sake J; Guzzetta, Giorgio; Hontelez, Jan A C; Horn, Johannes; Jepsen, Martin R; Kim, Jane J; Lazzarato, Fulvio; Matthijsse, Suzette M; Mikolajczyk, Rafael; Pavelyev, Andrew; Pillsbury, Matthew; Shafer, Leigh Anne; Tully, Stephen P; Turner, Hugo C; Usher, Cara; Walsh, Cathal
2016-11-01
Modelling studies have been widely used to inform human papillomavirus (HPV) vaccination policy decisions; however, many models exist and it is not known whether they produce consistent predictions of population-level effectiveness and herd effects. We did a systematic review and meta-analysis of model predictions of the long-term population-level effectiveness of vaccination against HPV 16, 18, 6, and 11 infection in women and men, to examine the variability in predicted herd effects, incremental benefit of vaccinating boys, and potential for HPV-vaccine-type elimination. We searched MEDLINE and Embase for transmission-dynamic modelling studies published between Jan 1, 2009, and April 28, 2015, that predicted the population-level impact of vaccination on HPV 6, 11, 16, and 18 infections in high-income countries. We contacted authors to determine whether they were willing to produce new predictions for standardised scenarios. Strategies investigated were girls-only vaccination and girls and boys vaccination at age 12 years. Base-case vaccine characteristics were 100% efficacy and lifetime protection. We did sensitivity analyses by varying vaccination coverage, vaccine efficacy, and duration of protection. For all scenarios we pooled model predictions of relative reductions in HPV prevalence (RR prev ) over time after vaccination and summarised results using the median and 10th and 90th percentiles (80% uncertainty intervals [UI]). 16 of 19 eligible models from ten high-income countries provided predictions. Under base-case assumptions, 40% vaccination coverage and girls-only vaccination, the RR prev of HPV 16 among women and men was 0·53 (80% UI 0·46-0·68) and 0·36 (0·28-0·61), respectively, after 70 years. With 80% girls-only vaccination coverage, the RR prev of HPV 16 among women and men was 0·93 (0·90-1·00) and 0·83 (0·75-1·00), respectively. Vaccinating boys in addition to girls increased the RR prev of HPV 16 among women and men by 0·18 (0·13-0
Untangling the Interplay between Epidemic Spread and Transmission Network Dynamics.
Directory of Open Access Journals (Sweden)
Christel Kamp
Full Text Available The epidemic spread of infectious diseases is ubiquitous and often has a considerable impact on public health and economic wealth. The large variability in the spatio-temporal patterns of epidemics prohibits simple interventions and requires a detailed analysis of each epidemic with respect to its infectious agent and the corresponding routes of transmission. To facilitate this analysis, we introduce a mathematical framework which links epidemic patterns to the topology and dynamics of the underlying transmission network. The evolution, both in disease prevalence and transmission network topology, is derived from a closed set of partial differential equations for infections without allowing for recovery. The predictions are in excellent agreement with complementarily conducted agent-based simulations. The capacity of this new method is demonstrated in several case studies on HIV epidemics in synthetic populations: it allows us to monitor the evolution of contact behavior among healthy and infected individuals and the contributions of different disease stages to the spreading of the epidemic. This gives both direction to and a test bed for targeted intervention strategies for epidemic control. In conclusion, this mathematical framework provides a capable toolbox for the analysis of epidemics from first principles. This allows for fast, in silico modeling--and manipulation--of epidemics and is especially powerful if complemented with adequate empirical data for parameterization.
Dynamic investigation of a locomotive with effect of gear transmissions under tractive conditions
Chen, Zaigang; Zhai, Wanming; Wang, Kaiyun
2017-11-01
Locomotive is used to drag trailers to move or supply the braking forces to slow the running speed of a train. The electromagnetic torque of the motor is always transmitted by the gear transmission system to the wheelset for generation of the tractive or braking forces at the wheel-rail contact interface. Consequently, gear transmission system is significant for power delivery of a locomotive. This paper develops a comprehensive locomotive-track vertical-longitudinal coupled dynamics model with dynamic effect of gear transmissions. This dynamics model enables considering the coupling interactions between the gear transmission motion, the vertical and the longitudinal motions of the vehicle, and the vertical vibration of the track structure. In this study, some complicated dynamic excitations, such as the gear time-varying mesh stiffness, nonlinear gear tooth backlash, the nonlinear wheel-rail normal contact force and creep force, and the rail vertical geometrical irregularity, are considered. Then, the dynamic responses of the locomotive under the tractive conditions are demonstrated by numerical simulations based on the established dynamics model and by experimental test. The developed dynamics model is validated by the good agreement between the experimental and the theoretical results. The calculated results reveal that the gear transmission system has strong dynamic interactions with the wheel-rail contact interface including both the vertical and the longitudinal motions, and it has negligible effect on the vibrations of the bogie frame and carbody.
Dynamic characteristic analysis of mother to child transmission of HIV in India
Directory of Open Access Journals (Sweden)
A. S. Kadi
2014-01-01
Full Text Available In this study, a mathematical model of HIV/AIDS mother to child transmission to analyze the effectiveness of prevention of HIV mother to child transmission programmes has been presented. The result reveals that prevention of HIV mother to child transmission programmes focusing only on biological transmission cannot control the increase of the HIV mother to child transmission in India. Hence, to control the HIV MTCT epidemic in India, in spite of strengthening the PMTCT programmes to reduce transmission rates, effective measures should be taken to prevent HIV infection in women of reproductive ages. Since the overall HIV MTCT epidemic is dependent on the HIV incidence in women of reproductive age group, the integration of pediatric HIV model with a detailed model of adult HIV would be investigated in future studies in order to model these dynamics more accurately.
Matrix of transmission in structural dynamics
International Nuclear Information System (INIS)
Mukherjee, S.
1975-01-01
The problem of close-coupled systems and cantilever type buildings can be treated efficiently by means of the very general and versatile method of transmission matrix. The expression 'matrix of transmission' is used to point out the fact that the method to be described differs fundamentally from another method related to matrix calculus, and also successfully used in vibration problem. In this method, forces and displacements are introduced as the 'unknowns' of the problem. The 'matrix of transmission' relates these quantities at one point of the structure to those at the neighbouring point. The natural frequencies of a freely vibrating elastic system can be found by applying proper end conditions. The end conditions will yield the frequency determinate to zero. By using suitable numerical method, the natural frequencies and mode shapes are determined, by making a frequency sweep within the range of interest. Results of analysis of a typical nuclear building by this method show very close agreement with the results obtained by using ASKA and SAP IV Program
Modelling the transmission of healthcare associated infections: a systematic review
2013-01-01
Background Dynamic transmission models are increasingly being used to improve our understanding of the epidemiology of healthcare-associated infections (HCAI). However, there has been no recent comprehensive review of this emerging field. This paper summarises how mathematical models have informed the field of HCAI and how methods have developed over time. Methods MEDLINE, EMBASE, Scopus, CINAHL plus and Global Health databases were systematically searched for dynamic mathematical models of HCAI transmission and/or the dynamics of antimicrobial resistance in healthcare settings. Results In total, 96 papers met the eligibility criteria. The main research themes considered were evaluation of infection control effectiveness (64%), variability in transmission routes (7%), the impact of movement patterns between healthcare institutes (5%), the development of antimicrobial resistance (3%), and strain competitiveness or co-colonisation with different strains (3%). Methicillin-resistant Staphylococcus aureus was the most commonly modelled HCAI (34%), followed by vancomycin resistant enterococci (16%). Other common HCAIs, e.g. Clostridum difficile, were rarely investigated (3%). Very few models have been published on HCAI from low or middle-income countries. The first HCAI model has looked at antimicrobial resistance in hospital settings using compartmental deterministic approaches. Stochastic models (which include the role of chance in the transmission process) are becoming increasingly common. Model calibration (inference of unknown parameters by fitting models to data) and sensitivity analysis are comparatively uncommon, occurring in 35% and 36% of studies respectively, but their application is increasing. Only 5% of models compared their predictions to external data. Conclusions Transmission models have been used to understand complex systems and to predict the impact of control policies. Methods have generally improved, with an increased use of stochastic models, and
Recasting the theory of mosquito-borne pathogen transmission dynamics and control
Smith, David L.; Perkins, T. Alex; Reiner, Robert C.; Barker, Christopher M.; Niu, Tianchan; Chaves, Luis Fernando; Ellis, Alicia M.; George, Dylan B.; Le Menach, Arnaud; Pulliam, Juliet R. C.; Bisanzio, Donal; Buckee, Caroline; Chiyaka, Christinah; Cummings, Derek A. T.; Garcia, Andres J.; Gatton, Michelle L.; Gething, Peter W.; Hartley, David M.; Johnston, Geoffrey; Klein, Eili Y.; Michael, Edwin; Lloyd, Alun L.; Pigott, David M.; Reisen, William K.; Ruktanonchai, Nick; Singh, Brajendra K.; Stoller, Jeremy; Tatem, Andrew J.; Kitron, Uriel; Godfray, H. Charles J.; Cohen, Justin M.; Hay, Simon I.; Scott, Thomas W.
2014-01-01
Mosquito-borne diseases pose some of the greatest challenges in public health, especially in tropical and sub-tropical regions of the world. Efforts to control these diseases have been underpinned by a theoretical framework developed for malaria by Ross and Macdonald, including models, metrics for measuring transmission, and theory of control that identifies key vulnerabilities in the transmission cycle. That framework, especially Macdonald's formula for R0 and its entomological derivative, vectorial capacity, are now used to study dynamics and design interventions for many mosquito-borne diseases. A systematic review of 388 models published between 1970 and 2010 found that the vast majority adopted the Ross–Macdonald assumption of homogeneous transmission in a well-mixed population. Studies comparing models and data question these assumptions and point to the capacity to model heterogeneous, focal transmission as the most important but relatively unexplored component in current theory. Fine-scale heterogeneity causes transmission dynamics to be nonlinear, and poses problems for modeling, epidemiology and measurement. Novel mathematical approaches show how heterogeneity arises from the biology and the landscape on which the processes of mosquito biting and pathogen transmission unfold. Emerging theory focuses attention on the ecological and social context for mosquito blood feeding, the movement of both hosts and mosquitoes, and the relevant spatial scales for measuring transmission and for modeling dynamics and control. PMID:24591453
Recasting the theory of mosquito-borne pathogen transmission dynamics and control.
Smith, David L; Perkins, T Alex; Reiner, Robert C; Barker, Christopher M; Niu, Tianchan; Chaves, Luis Fernando; Ellis, Alicia M; George, Dylan B; Le Menach, Arnaud; Pulliam, Juliet R C; Bisanzio, Donal; Buckee, Caroline; Chiyaka, Christinah; Cummings, Derek A T; Garcia, Andres J; Gatton, Michelle L; Gething, Peter W; Hartley, David M; Johnston, Geoffrey; Klein, Eili Y; Michael, Edwin; Lloyd, Alun L; Pigott, David M; Reisen, William K; Ruktanonchai, Nick; Singh, Brajendra K; Stoller, Jeremy; Tatem, Andrew J; Kitron, Uriel; Godfray, H Charles J; Cohen, Justin M; Hay, Simon I; Scott, Thomas W
2014-04-01
Mosquito-borne diseases pose some of the greatest challenges in public health, especially in tropical and sub-tropical regions of the world. Efforts to control these diseases have been underpinned by a theoretical framework developed for malaria by Ross and Macdonald, including models, metrics for measuring transmission, and theory of control that identifies key vulnerabilities in the transmission cycle. That framework, especially Macdonald's formula for R0 and its entomological derivative, vectorial capacity, are now used to study dynamics and design interventions for many mosquito-borne diseases. A systematic review of 388 models published between 1970 and 2010 found that the vast majority adopted the Ross-Macdonald assumption of homogeneous transmission in a well-mixed population. Studies comparing models and data question these assumptions and point to the capacity to model heterogeneous, focal transmission as the most important but relatively unexplored component in current theory. Fine-scale heterogeneity causes transmission dynamics to be nonlinear, and poses problems for modeling, epidemiology and measurement. Novel mathematical approaches show how heterogeneity arises from the biology and the landscape on which the processes of mosquito biting and pathogen transmission unfold. Emerging theory focuses attention on the ecological and social context for mosquito blood feeding, the movement of both hosts and mosquitoes, and the relevant spatial scales for measuring transmission and for modeling dynamics and control.
Energy Technology Data Exchange (ETDEWEB)
Teles, Francisco A.S.; Santos, Ebenezer F.; Dantas, Carlos C., E-mail: francisco.teles@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Centro de Tecnologia e Geociencias. Departamento de Energia Nuclear; Melo, Silvio B., E-mail: sbm@cin.ufpe.br [Universidade Federal de Pernambuco (CIN/UFPE), Recife, PE (Brazil). Centro de Informatica; Santos, Valdemir A. dos, E-mail: vas@unicap.br [Universidade Catolica de Pernambuco (UNICAP), Recife, PE (Brazil). Dept. de Quimica; Lima, Emerson A.O., E-mail: emathematics@gmail.com [Universidade de Pernambuco (POLI/UPE), Recife, PE (Brazil). Escola Politecnica
2013-07-01
In this paper, fluid dynamics of Fluid Catalytic Cracking (FCC) process is investigated by means of a Cold Flow Pilot Unit (CFPU) constructed in Plexiglas to visualize operational conditions. Axial and radial catalyst profiles were measured by gamma ray transmission in the riser of the CFPU. Standard uncertainty was evaluated in volumetric solid fraction measurements for several concentrations at a given point of axial profile. Monitoring of the pressure drop in riser shows a good agreement with measured standard uncertainty data. A further evaluation of the combined uncertainty was applied to volumetric solid fraction equation using gamma transmission data. Limit condition of catalyst concentration in riser was defined and simulation with random numbers provided by MATLAB software has tested uncertainty evaluation. The Guide to the expression of Uncertainty in Measurement (GUM) is based on the law of propagation of uncertainty and on the characterization of the quantities measured by means of either a Gaussian distribution or a t-distribution, which allows measurement uncertainty to be delimited by means of a confidence interval. A variety of supplements to GUM are being developed, which will progressively enter into effect. The first of these supplements [3] describes an alternative procedure for the calculation of uncertainties: the Monte Carlo Method (MCM).MCM is an alternative to GUM, since it performs a characterization of the quantities measured based on the random sampling of the probability distribution functions. This paper also explains the basic implementation of the MCM method in MATLAB. (author)
International Nuclear Information System (INIS)
Teles, Francisco A.S.; Santos, Ebenezer F.; Dantas, Carlos C.; Melo, Silvio B.; Santos, Valdemir A. dos; Lima, Emerson A.O.
2013-01-01
In this paper, fluid dynamics of Fluid Catalytic Cracking (FCC) process is investigated by means of a Cold Flow Pilot Unit (CFPU) constructed in Plexiglas to visualize operational conditions. Axial and radial catalyst profiles were measured by gamma ray transmission in the riser of the CFPU. Standard uncertainty was evaluated in volumetric solid fraction measurements for several concentrations at a given point of axial profile. Monitoring of the pressure drop in riser shows a good agreement with measured standard uncertainty data. A further evaluation of the combined uncertainty was applied to volumetric solid fraction equation using gamma transmission data. Limit condition of catalyst concentration in riser was defined and simulation with random numbers provided by MATLAB software has tested uncertainty evaluation. The Guide to the expression of Uncertainty in Measurement (GUM) is based on the law of propagation of uncertainty and on the characterization of the quantities measured by means of either a Gaussian distribution or a t-distribution, which allows measurement uncertainty to be delimited by means of a confidence interval. A variety of supplements to GUM are being developed, which will progressively enter into effect. The first of these supplements [3] describes an alternative procedure for the calculation of uncertainties: the Monte Carlo Method (MCM).MCM is an alternative to GUM, since it performs a characterization of the quantities measured based on the random sampling of the probability distribution functions. This paper also explains the basic implementation of the MCM method in MATLAB. (author)
Directory of Open Access Journals (Sweden)
Nicky McCreesh
Full Text Available There is increasing interest in the control and elimination of schistosomiasis. Little is known, however, about the likely effects of increasing water-body temperatures on transmission.We have developed an agent-based model of the temperature-sensitive stages of the Schistosoma and intermediate host snail life-cycles, parameterised using data from S. mansoni and Biomphalaria pfeifferi laboratory and field-based observations. Infection risk is calculated as the number of cercariae in the model, adjusted for their probability of causing infection.The number of snails in the model is approximately constant between 15-31°C. Outside this range, snail numbers drop sharply, and the snail population cannot survive outside the range 14-32°C. Mean snail generation time decreases with increasing temperature from 176 days at 14°C to 46 days at 26°C. Human infection risk is highest between 16-18°C and 1pm and 6-10pm in calm water, and 20-25°C and 12-4pm in flowing water. Infection risk increases sharply when temperatures increase above the minimum necessary for sustained transmission.The model suggests that, in areas where S. mansoni is already endemic, warming of the water at transmission sites will have differential effects on both snails and parasites depending on abiotic properties of the water-body. Snail generation times will decrease in most areas, meaning that snail populations will recover faster from natural population reductions and from snail-control efforts. We suggest a link between the ecological properties of transmission sites and infection risk which could significantly affect the outcomes of interventions designed to alter water contact behaviour--proposing that such interventions are more likely to reduce infection levels at river locations than lakes, where infection risk remains high for longer. In cooler areas where snails are currently found, increasing temperatures may significantly increase infection risk, potentially leading
Transmission Dynamics and Optimal Control of Malaria in Kenya
Directory of Open Access Journals (Sweden)
Gabriel Otieno
2016-01-01
Full Text Available This paper proposes and analyses a mathematical model for the transmission dynamics of malaria with four-time dependent control measures in Kenya: insecticide treated bed nets (ITNs, treatment, indoor residual spray (IRS, and intermittent preventive treatment of malaria in pregnancy (IPTp. We first considered constant control parameters and calculate the basic reproduction number and investigate existence and stability of equilibria as well as stability analysis. We proved that if R0≤1, the disease-free equilibrium is globally asymptotically stable in D. If R0>1, the unique endemic equilibrium exists and is globally asymptotically stable. The model also exhibits backward bifurcation at R0=1. If R0>1, the model admits a unique endemic equilibrium which is globally asymptotically stable in the interior of feasible region D. The sensitivity results showed that the most sensitive parameters are mosquito death rate and mosquito biting rates. We then consider the time-dependent control case and use Pontryagin’s Maximum Principle to derive the necessary conditions for the optimal control of the disease using the proposed model. The existence of optimal control problem is proved. Numerical simulations of the optimal control problem using a set of reasonable parameter values suggest that the optimal control strategy for malaria control in endemic areas is the combined use of treatment and IRS; for epidemic prone areas is the use of treatment and IRS; for seasonal areas is the use of treatment; and for low risk areas is the use of ITNs and treatment. Control programs that follow these strategies can effectively reduce the spread of malaria disease in different malaria transmission settings in Kenya.
Effect of the one-child policy on influenza transmission in China: a stochastic transmission model.
Directory of Open Access Journals (Sweden)
Fengchen Liu
Full Text Available BACKGROUND: China's one-child-per-couple policy, introduced in 1979, led to profound demographic changes for nearly a quarter of the world's population. Several decades later, the consequences include decreased fertility rates, population aging, decreased household sizes, changes in family structure, and imbalanced sex ratios. The epidemiology of communicable diseases may have been affected by these changes since the transmission dynamics of infectious diseases depend on demographic characteristics of the population. Of particular interest is influenza because China and Southeast Asia lie at the center of a global transmission network of influenza. Moreover, changes in household structure may affect influenza transmission. Is it possible that the pronounced demographic changes that have occurred in China have affected influenza transmission? METHODS AND FINDINGS: To address this question, we developed a continuous-time, stochastic, individual-based simulation model for influenza transmission. With this model, we simulated 30 years of influenza transmission and compared influenza transmission rates in populations with and without the one-child policy control. We found that the average annual attack rate is reduced by 6.08% (SD 2.21% in the presence of the one-child policy compared to a population in which no demographic changes occurred. There was no discernible difference in the secondary attack rate, -0.15% (SD 1.85%, between the populations with and without a one-child policy. We also forecasted influenza transmission over a ten-year time period in a population with a two-child policy under a hypothesis that a two-child-per-couple policy will be carried out in 2015, and found a negligible difference in the average annual attack rate compared to the population with the one-child policy. CONCLUSIONS: This study found that the average annual attack rate is slightly lowered in a population with a one-child policy, which may have resulted from a
Saad, Neil J; Bowles, Cayley C; Grenfell, Bryan T; Basnyat, Buddha; Arjyal, Amit; Dongol, Sabina; Karkey, Abhilasha; Baker, Stephen; Pitzer, Virginia E
2017-05-01
A substantial proportion of the global burden of typhoid fever occurs in South Asia. Kathmandu, Nepal experienced a substantial increase in the number of typhoid fever cases (caused by Salmonella Typhi) between 2000 and 2003, which subsequently declined but to a higher endemic level than in 2000. This epidemic of S. Typhi coincided with an increase in organisms with reduced susceptibility against fluoroquinolones, the emergence of S. Typhi H58, and an increase in the migratory population in Kathmandu. We devised a mathematical model to investigate the potential epidemic drivers of typhoid in Kathmandu and fit this model to weekly data of S. Typhi cases between April 1997 and June 2011 and the age distribution of S. Typhi cases. We used this model to determine if the typhoid epidemic in Kathmandu was driven by heightened migration, the emergence of organisms with reduced susceptibility against fluoroquinolones or a combination of these factors. Models allowing for the migration of susceptible individuals into Kathmandu alone or in combination with the emergence of S. Typhi with reduced susceptibility against fluoroquinolones provided a good fit for the data. The emergence of organisms with reduced susceptibility against fluoroquinolones organisms alone, either through an increase in disease duration or increased transmission, did not fully explain the pattern of S. Typhi infections. Our analysis is consistent with the hypothesis that the increase in typhoid fever in Kathmandu was associated with the migration of susceptible individuals into the city and aided by the emergence of reduced susceptibility against fluoroquinolones. These data support identifying and targeting migrant populations with typhoid immunization programmes to prevent transmission and disease.
Analyzing transmission dynamics of cholera with public health interventions.
Posny, Drew; Wang, Jin; Mukandavire, Zindoga; Modnak, Chairat
2015-06-01
Cholera continues to be a serious public health concern in developing countries and the global increase in the number of reported outbreaks suggests that activities to control the diseases and surveillance programs to identify or predict the occurrence of the next outbreaks are not adequate. These outbreaks have increased in frequency, severity, duration and endemicity in recent years. Mathematical models for infectious diseases play a critical role in predicting and understanding disease mechanisms, and have long provided basic insights in the possible ways to control infectious diseases. In this paper, we present a new deterministic cholera epidemiological model with three types of control measures incorporated into a cholera epidemic setting: treatment, vaccination and sanitation. Essential dynamical properties of the model with constant intervention controls which include local and global stabilities for the equilibria are carefully analyzed. Further, using optimal control techniques, we perform a study to investigate cost-effective solutions for time-dependent public health interventions in order to curb disease transmission in epidemic settings. Our results show that the basic reproductive number (R0) remains the model's epidemic threshold despite the inclusion of a package of cholera interventions. For time-dependent controls, the results suggest that these interventions closely interplay with each other, and the costs of controls directly affect the length and strength of each control in an optimal strategy. Copyright © 2015 Elsevier Inc. All rights reserved.
Nipah virus transmission in a hamster model.
Directory of Open Access Journals (Sweden)
Emmie de Wit
2011-12-01
Full Text Available Based on epidemiological data, it is believed that human-to-human transmission plays an important role in Nipah virus outbreaks. No experimental data are currently available on the potential routes of human-to-human transmission of Nipah virus. In a first dose-finding experiment in Syrian hamsters, it was shown that Nipah virus was predominantly shed via the respiratory tract within nasal and oropharyngeal secretions. Although Nipah viral RNA was detected in urogenital and rectal swabs, no infectious virus was recovered from these samples, suggesting no viable virus was shed via these routes. In addition, hamsters inoculated with high doses shed significantly higher amounts of viable Nipah virus particles in comparison with hamsters infected with lower inoculum doses. Using the highest inoculum dose, three potential routes of Nipah virus transmission were investigated in the hamster model: transmission via fomites, transmission via direct contact and transmission via aerosols. It was demonstrated that Nipah virus is transmitted efficiently via direct contact and inefficiently via fomites, but not via aerosols. These findings are in line with epidemiological data which suggest that direct contact with nasal and oropharyngeal secretions of Nipah virus infected individuals resulted in greater risk of Nipah virus infection. The data provide new and much-needed insights into the modes and efficiency of Nipah virus transmission and have important public health implications with regards to the risk assessment and management of future Nipah virus outbreaks.
Modeling of Viral Aerosol Transmission and Detection
Khalid, Maryam; Amin, Osama; Ahmed, Sajid; Alouini, Mohamed-Slim
2018-01-01
The objective of this work is to investigate the spread mechanism of diseases in the atmosphere as an engineering problem. Among the viral transmission mechanisms that do not include physical contact, aerosol transmission is the most significant mode of transmission where virus-laden droplets are carried over long distances by wind. In this work, we focus on aerosol transmission of virus and introduce the idea of viewing virus transmission through aerosols and their transport as a molecular communication problem, where one has no control over transmission source but a robust receiver can be designed using nano-biosensors. To investigate this idea, a complete system is presented and end-toend mathematical model for the aerosol transmission channel is derived under certain constraints and boundary conditions. In addition to transmitter and channel, a receiver architecture composed of air sampler and Silicon Nanowire field effect transistor is also discussed. Furthermore, a detection problem is formulated for which maximum likelihood decision rule and the corresponding missed detection probability is discussed. At the end, simulation results are presented to investigate the parameters that affect the performance and justify the feasibility of proposed setup in related applications.
Transmission dynamics of malaria in Nigeria. | Okwa | Annals of ...
African Journals Online (AJOL)
Background: Two of the problems of malaria parasite vector control in Nigeria are the diversity of Anopheline vectors and large size of the country. Anopheline distribution and transmission dynamics of malaria were therefore compared between four ecotypes in Nigeria during the rainy season. Methods: Polymerase chain ...
Forecasting Ebola with a regression transmission model
Asher, Jason
2017-01-01
We describe a relatively simple stochastic model of Ebola transmission that was used to produce forecasts with the lowest mean absolute error among Ebola Forecasting Challenge participants. The model enabled prediction of peak incidence, the timing of this peak, and final size of the outbreak. The underlying discrete-time compartmental model used a time-varying reproductive rate modeled as a multiplicative random walk driven by the number of infectious individuals. This structure generalizes ...
Deterministic and stochastic CTMC models from Zika disease transmission
Zevika, Mona; Soewono, Edy
2018-03-01
Zika infection is one of the most important mosquito-borne diseases in the world. Zika virus (ZIKV) is transmitted by many Aedes-type mosquitoes including Aedes aegypti. Pregnant women with the Zika virus are at risk of having a fetus or infant with a congenital defect and suffering from microcephaly. Here, we formulate a Zika disease transmission model using two approaches, a deterministic model and a continuous-time Markov chain stochastic model. The basic reproduction ratio is constructed from a deterministic model. Meanwhile, the CTMC stochastic model yields an estimate of the probability of extinction and outbreaks of Zika disease. Dynamical simulations and analysis of the disease transmission are shown for the deterministic and stochastic models.
Peterson, Jennifer K; Bartsch, Sarah M; Lee, Bruce Y; Dobson, Andrew P
2015-10-22
Chagas disease (caused by Trypanosoma cruzi) is the most important neglected tropical disease (NTD) in Latin America, infecting an estimated 5.7 million people in the 21 countries where it is endemic. It is one of the NTDs targeted for control and elimination by the 2020 London Declaration goals, with the first goal being to interrupt intra-domiciliary vector-borne T. cruzi transmission. A key question in domestic T. cruzi transmission is the role that synanthropic animals play in T. cruzi transmission to humans. Here, we ask, (1) do synanthropic animals need to be targeted in Chagas disease prevention policies?, and (2) how does the presence of animals affect the efficacy of vector control? We developed a simple mathematical model to simulate domestic vector-borne T. cruzi transmission and to specifically examine the interaction between the presence of synanthropic animals and effects of vector control. We used the model to explore how the interactions between triatomine bugs, humans and animals impact the number and proportion of T. cruzi-infected bugs and humans. We then examined how T. cruzi dynamics change when control measures targeting vector abundance are introduced into the system. We found that the presence of synanthropic animals slows the speed of T. cruzi transmission to humans, and increases the sensitivity of T. cruzi transmission dynamics to vector control measures at comparable triatomine carrying capacities. However, T. cruzi transmission is amplified when triatomine carrying capacity increases with the abundance of syntathoropic hosts. Our results suggest that in domestic T. cruzi transmission scenarios where no vector control measures are in place, a reduction in synanthropic animals may slow T. cruzi transmission to humans, but it would not completely eliminate transmission. To reach the 2020 goal of interrupting intra-domiciliary T. cruzi transmission, it is critical to target vector populations. Additionally, where vector control measures
Molecular Modeling of Prion Transmission to Humans
Directory of Open Access Journals (Sweden)
Etienne Levavasseur
2014-10-01
Full Text Available Using different prion strains, such as the variant Creutzfeldt-Jakob disease agent and the atypical bovine spongiform encephalopathy agents, and using transgenic mice expressing human or bovine prion protein, we assessed the reliability of protein misfolding cyclic amplification (PMCA to model interspecies and genetic barriers to prion transmission. We compared our PMCA results with in vivo transmission data characterized by attack rates, i.e., the percentage of inoculated mice that developed the disease. Using 19 seed/substrate combinations, we observed that a significant PMCA amplification was only obtained when the mouse line used as substrate is susceptible to the corresponding strain. Our results suggest that PMCA provides a useful tool to study genetic barriers to transmission and to study the zoonotic potential of emerging prion strains.
Dynamic sex roles among men who have sex with men and transmissions from primary HIV infection.
Alam, Shah Jamal; Romero-Severson, Ethan; Kim, Jong-Hoon; Emond, Gilbert; Koopman, James S
2010-09-01
Previous studies estimating the fraction of transmissions from persons with primary HIV have not focused on the effects of switching sex role in male homosexual populations. Such behavioral fluctuations can increase the contribution of primary HIV in the overall population. We modeled HIV transmission with 8 compartments defined by 4 behavioral groups, with different anal-insertive and anal-receptive combinations, and 2 stages of infection. We explored the effects of fluctuating behavioral categories on endemic prevalence and the fraction of transmissions from primary HIV. We varied transition rates to develop the theory on how behavioral fluctuation affects infection patterns, and we used the transition rates in a Netherlands cohort to assess overall effects in a real setting. The dynamics of change in behavior-group status over time observed in the Netherlands cohort amplifies the prevalence of infection and the fraction of transmissions from primary HIV, resulting in the highest proportions of transmissions being from people with primary HIV. Fluctuation between dual- or receptive-role periods and no-anal-sex periods mainly determines this amplification. In terms of the total transmissions, the dual-role risk group is dominant. Fluctuation between insertive and receptive roles decreases the fraction of transmissions from primary HIV, but such fluctuation is infrequently observed. The fraction of transmissions from primary HIV is considerably raised by fluctuations in insertive and receptive anal sex behaviors. This increase occurs even when primary HIV or later infection status does not influence risk behavior. Thus, it is not simply biology but also behavior patterns and social contexts that determine the fraction of transmissions from primary HIV. Moreover, each primary HIV transmission has a larger population effect than each later infection transmission because the men to whom one transmits from primary HIV carry on more chains of transmissions than the men
Singh, Rajendra; Houser, Donald R.
1993-01-01
This paper discusses analytical and experimental approaches that will be needed to understand dynamic, vibro-acoustic and design characteristics of high power density rotorcraft transmissions. Complexities associated with mathematical modeling of such systems will be discussed. An overview of research work planned during the next several years will be presented, with emphasis on engineering science issues such as gear contact mechanics, multi-mesh drive dynamics, parameter uncertainties, vibration transmission through bearings, and vibro-acoustic characteristics of geared rotor systems and housing-mount structures. A few examples of work in progress are cited.
A review of malaria transmission dynamics in forest ecosystems
2014-01-01
Malaria continues to be a major health problem in more than 100 endemic countries located primarily in tropical and sub-tropical regions around the world. Malaria transmission is a dynamic process and involves many interlinked factors, from uncontrollable natural environmental conditions to man-made disturbances to nature. Almost half of the population at risk of malaria lives in forest areas. Forests are hot beds of malaria transmission as they provide conditions such as vegetation cover, temperature, rainfall and humidity conditions that are conducive to distribution and survival of malaria vectors. Forests often lack infrastructure and harbor tribes with distinct genetic traits, socio-cultural beliefs and practices that greatly influence malaria transmission dynamics. Here we summarize the various topographical, entomological, parasitological, human ecological and socio-economic factors, which are crucial and shape malaria transmission in forested areas. An in-depth understanding and synthesis of the intricate relationship of these parameters in achieving better malaria control in various types of forest ecosystems is emphasized. PMID:24912923
X-ray transmission movies of spontaneous dynamic events
International Nuclear Information System (INIS)
Smilowitz, L.; Henson, B. F.; Holmes, M.; Novak, A.; Oschwald, D.; Dolgonos, P.; Qualls, B.
2014-01-01
We describe a new x-ray radiographic imaging system which allows for continuous x-ray transmission imaging of spontaneous dynamic events. We demonstrate this method on thermal explosions in three plastic bonded formulations of the energetic material octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. We describe the x-ray imaging system and triggering developed to enable the continuous imaging of a thermal explosion
Molecular dynamics of TBP and DBP studied by neutron transmission
International Nuclear Information System (INIS)
Salles Filho, J.B.V.; Refinetti, M.E.; Fulfaro, R.; Vinhas, L.A.
1984-04-01
Differences between the properties of TBP and DBP, concerning the uranium extraction processes, may be related to certain characteristics of the molecular dynamics of each compound. In order to investigate the dynamical behaviour of hydrogen in these molecules, neutron transmission of TBP and DBP has been measured as a function of neutron wavelenght in the range 4.0 - 6.0 A, at room temperature. Scattering cross sections per hydrogen atom have been obtained. From the comparison with results previously obtained for n-butanol, similar dynamical behaviour of butyl radicals in these compounds could be observed. This similarity indicates that the presence of two or three butyl radicals in butylphosphate molecules does not exert influence in the hydrogen motion of methyl and methylene groups. This suggests that the different chemical behaviour between TBP and DBP is related to the dynamics of the hydrogen directly bound to the DBP phosphate group.(Author) [pt
Ghanem, Bernard; Ahuja, Narendra
2013-01-01
This paper proposes the problem of modeling video sequences of dynamic swarms (DSs). We define a DS as a large layout of stochastically repetitive spatial configurations of dynamic objects (swarm elements) whose motions exhibit local spatiotemporal
Bifurcation analysis of dengue transmission model in Baguio City, Philippines
Libatique, Criselda P.; Pajimola, Aprimelle Kris J.; Addawe, Joel M.
2017-11-01
In this study, we formulate a deterministic model for the transmission dynamics of dengue fever in Baguio City, Philippines. We analyzed the existence of the equilibria of the dengue model. We computed and obtained conditions for the existence of the equilibrium states. Stability analysis for the system is carried out for disease free equilibrium. We showed that the system becomes stable under certain conditions of the parameters. A particular parameter is taken and with the use of the Theory of Centre Manifold, the proposed model demonstrates a bifurcation phenomenon. We performed numerical simulation to verify the analytical results.
Dynamic analysis of spiral bevel and hypoid gears with high-order transmission errors
Yang, J. J.; Shi, Z. H.; Zhang, H.; Li, T. X.; Nie, S. W.; Wei, B. Y.
2018-03-01
A new gear surface modification methodology based on curvature synthesis is proposed in this study to improve the transmission performance. The generated high-order transmission error (TE) for spiral bevel and hypoid gears is proved to reduce the vibration of geared-rotor system. The method is comprised of the following steps: Firstly, the fully conjugate gear surfaces with pinion flank modified according to the predesigned relative transmission movement are established based on curvature correction. Secondly, a 14-DOF geared-rotor system model considering backlash nonlinearity is used to evaluate the effect of different orders of TE on the dynamic performance a hypoid gear transmission system. For case study, numerical simulation is performed to illustrate the dynamic response of hypoid gear pair with parabolic, fourth-order and sixth-order transmission error derived. The results show that the parabolic TE curve has higher peak to peak amplitude compared to the other two types of TE. Thus, the excited dynamic response also shows larger amplitude at response peaks. Dynamic responses excited by fourth and sixth order TE also demonstrate distinct response components due to their different TE period which is expected to generate different sound quality or other acoustic characteristics.
Modelling of volatility in monetary transmission mechanism
Energy Technology Data Exchange (ETDEWEB)
Dobešová, Anna; Klepáč, Václav; Kolman, Pavel [Department of Statistics and Operation Analysis, Faculty of Business and Economics, Mendel University in Brno, Zemědělská 1, 61300, Brno (Czech Republic); Bednářová, Petra [Institute of Technology and Business, Okružní 517/10, 370 01, České Budějovice (Czech Republic)
2015-03-10
The aim of this paper is to compare different approaches to modeling of volatility in monetary transmission mechanism. For this purpose we built time-varying parameter VAR (TVP-VAR) model with stochastic volatility and VAR-DCC-GARCH model with conditional variance. The data from three European countries are included in the analysis: the Czech Republic, Germany and Slovakia. Results show that VAR-DCC-GARCH system captures higher volatility of observed variables but main trends and detected breaks are generally identical in both approaches.
Modelling of volatility in monetary transmission mechanism
International Nuclear Information System (INIS)
Dobešová, Anna; Klepáč, Václav; Kolman, Pavel; Bednářová, Petra
2015-01-01
The aim of this paper is to compare different approaches to modeling of volatility in monetary transmission mechanism. For this purpose we built time-varying parameter VAR (TVP-VAR) model with stochastic volatility and VAR-DCC-GARCH model with conditional variance. The data from three European countries are included in the analysis: the Czech Republic, Germany and Slovakia. Results show that VAR-DCC-GARCH system captures higher volatility of observed variables but main trends and detected breaks are generally identical in both approaches
Dynamics of Pertussis Transmission in the United States
Magpantay, F. M. G.; Rohani, P.
2015-01-01
Past patterns of infectious disease transmission set the stage on which modern epidemiologic dynamics are played out. Here, we present a comprehensive account of pertussis (whooping cough) transmission in the United States during the early vaccine era. We analyzed recently digitized weekly incidence records from Morbidity and Mortality Weekly Reports from 1938 to 1955, when the whole-cell pertussis vaccine was rolled out, and related them to contemporary patterns of transmission and resurgence documented in monthly incidence data from the National Notifiable Diseases Surveillance System. We found that, during the early vaccine era, pertussis epidemics in US states could be categorized as 1) annual, 2) initially annual and later multiennial, or 3) multiennial. States with predominantly annual cycles tended to have higher per capita birth rates, more household crowding, more children per family, and lower rates of school attendance than the states with multiennial cycles. Additionally, states that exhibited annual epidemics during 1938–1955 have had the highest recent (2001–2010) incidence, while those states that transitioned from annual cycles to multiennial cycles have had relatively low recent incidence. Our study provides an extensive picture of pertussis epidemiology in the United States dating back to the onset of vaccination, a back-story that could aid epidemiologists in understanding contemporary transmission patterns. PMID:26022662
Dynamic Latent Classification Model
DEFF Research Database (Denmark)
Zhong, Shengtong; Martínez, Ana M.; Nielsen, Thomas Dyhre
as possible. Motivated by this problem setting, we propose a generative model for dynamic classification in continuous domains. At each time point the model can be seen as combining a naive Bayes model with a mixture of factor analyzers (FA). The latent variables of the FA are used to capture the dynamics...
Realistic modeling of radiation transmission inspection systems
International Nuclear Information System (INIS)
Sale, K.E.
1993-01-01
We have applied Monte Carlo particle transport methods to assess a proposed neutron transmission inspection system for checked luggage. The geometry of the system and the time, energy and angle dependence of the source have been modeled in detail. A pulsed deuteron beam incident on a thick Be target generates a neutron pulse with a very broad energy spectrum which is detected after passage through the luggage item by a plastic scintillator detector operating in current mode (as opposed to pulse counting mode). The neutron transmission as a function of time information is used to infer the densities of hydrogen, carbon, oxygen and nitrogen in the volume sampled. The measured elemental densities can be compared to signatures for explosives or other contraband. By using such computational modeling it is possible to optimize many aspects of the design of an inspection system without costly and time consuming prototyping experiments or to determine that a proposed scheme will not work. The methods applied here can be used to evaluate neutron or photon schemes based on transmission, scattering or reaction techniques
Thrall, P.H.; Biere, A.; Uyenoyama, M.K.
1995-01-01
Models incorporating density-dependent disease transmission functions generally provide a good fit for airborne and directly transmitted bacterial or viral diseases. However, the transmission dynamics of sexually transmitted and vector-borne diseases are likely to be frequency- rather than density-
Molenaar, Peter C M
2017-01-01
Equivalences of two classes of dynamic models for weakly stationary multivariate time series are discussed: dynamic factor models and autoregressive models. It is shown that exploratory dynamic factor models can be rotated, yielding an infinite set of equivalent solutions for any observed series. It also is shown that dynamic factor models with lagged factor loadings are not equivalent to the currently popular state-space models, and that restriction of attention to the latter type of models may yield invalid results. The known equivalent vector autoregressive model types, standard and structural, are given a new interpretation in which they are conceived of as the extremes of an innovating type of hybrid vector autoregressive models. It is shown that consideration of hybrid models solves many problems, in particular with Granger causality testing.
Kim, Yunhwan; Lee, Sunmi; Chu, Chaeshin; Choe, Seoyun; Hong, Saeme; Shin, Youngseo
2016-02-01
The outbreak of Middle Eastern respiratory syndrome coronavirus (MERS-CoV) was one of the major events in South Korea in 2015. In particular, this study pays attention to formulating a mathematical model for MERS transmission dynamics and estimating transmission rates. Incidence data of MERS-CoV from the government authority was analyzed for the first aim and a mathematical model was built and analyzed for the second aim of the study. A mathematical model for MERS-CoV transmission dynamics is used to estimate the transmission rates in two periods due to the implementation of intensive interventions. Using the estimates of the transmission rates, the basic reproduction number was estimated in two periods. Due to the superspreader, the basic reproduction number was very large in the first period; however, the basic reproduction number of the second period has reduced significantly after intensive interventions. It turned out to be the intensive isolation and quarantine interventions that were the most critical factors that prevented the spread of the MERS outbreak. The results are expected to be useful to devise more efficient intervention strategies in the future.
Flexible AC transmission systems modelling and control
Zhang, Xiao-Ping; Pal, Bikash
2012-01-01
The extended and revised second edition of this successful monograph presents advanced modeling, analysis and control techniques of Flexible AC Transmission Systems (FACTS). The book covers comprehensively a range of power-system control problems: from steady-state voltage and power flow control, to voltage and reactive power control, to voltage stability control, to small signal stability control using FACTS controllers. In the six years since the first edition of the book has been published research on the FACTS has continued to flourish while renewable energy has developed into a mature and
Transmission Dynamics of Methicillin-Resistant Staphylococcus aureus in Pigs
Crombé, Florence; Argudín, M. Angeles; Vanderhaeghen, Wannes; Hermans, Katleen; Haesebrouck, Freddy; Butaye, Patrick
2013-01-01
From the mid-2000s on, numerous studies have shown that methicillin-resistant Staphylococcus aureus (MRSA), renowned as human pathogen, has a reservoir in pigs and other livestock. In Europe and North America, clonal complex (CC) 398 appears to be the predominant lineage involved. Especially worrisome is its capacity to contaminate humans in close contact with affected animals. Indeed, the typical multi-resistant phenotype of MRSA CC398 and its observed ability of easily acquiring genetic material suggests that MRSA CC398 strains with an increased virulence potential may emerge, for which few therapeutic options would remain. This questions the need to implement interventions to control the presence and spread of MRSA CC398 among pigs. MRSA CC398 shows a high but not fully understood transmission potential in the pig population and is able to persist within that population. Although direct contact is probably the main route for MRSA transmission between pigs, also environmental contamination, the presence of other livestock, the herd size, and farm management are factors that may be involved in the dissemination of MRSA CC398. The current review aims at summarizing the research that has so far been done on the transmission dynamics and risk factors for introduction and persistence of MRSA CC398 in farms. PMID:23518663
Plasmodium vivax Population Structure and Transmission Dynamics in Sabah Malaysia
Abdullah, Noor Rain; Barber, Bridget E.; William, Timothy; Norahmad, Nor Azrina; Satsu, Umi Rubiah; Muniandy, Prem Kumar; Ismail, Zakiah; Grigg, Matthew J.; Jelip, Jenarun; Piera, Kim; von Seidlein, Lorenz; Yeo, Tsin W.; Anstey, Nicholas M.; Price, Ric N.; Auburn, Sarah
2013-01-01
Despite significant progress in the control of malaria in Malaysia, the complex transmission dynamics of P. vivax continue to challenge national efforts to achieve elimination. To assess the impact of ongoing interventions on P. vivax transmission dynamics in Sabah, we genotyped 9 short tandem repeat markers in a total of 97 isolates (8 recurrences) from across Sabah, with a focus on two districts, Kota Marudu (KM, n = 24) and Kota Kinabalu (KK, n = 21), over a 2 year period. STRUCTURE analysis on the Sabah-wide dataset demonstrated multiple sub-populations. Significant differentiation (F ST = 0.243) was observed between KM and KK, located just 130 Km apart. Consistent with low endemic transmission, infection complexity was modest in both KM (mean MOI = 1.38) and KK (mean MOI = 1.19). However, population diversity remained moderate (H E = 0.583 in KM and H E = 0.667 in KK). Temporal trends revealed clonal expansions reflecting epidemic transmission dynamics. The haplotypes of these isolates declined in frequency over time, but persisted at low frequency throughout the study duration. A diverse array of low frequency isolates were detected in both KM and KK, some likely reflecting remnants of previous expansions. In accordance with clonal expansions, high levels of Linkage Disequilibrium (I A S >0.5 [P<0.0001] in KK and KM) declined sharply when identical haplotypes were represented once (I A S = 0.07 [P = 0.0076] in KM, and I A S = -0.003 [P = 0.606] in KK). All 8 recurrences, likely to be relapses, were homologous to the prior infection. These recurrences may promote the persistence of parasite lineages, sustaining local diversity. In summary, Sabah's shrinking P. vivax population appears to have rendered this low endemic setting vulnerable to epidemic expansions. Migration may play an important role in the introduction of new parasite strains leading to epidemic expansions, with important implications for malaria
The influence of engine/transmission/governor on tilting proprotor aircraft dynamics
Johnson, W.
1975-01-01
An analytical model is developed for the dynamics of a tilting proprotor aircraft engine and drive train, including a rotor speed governor and interconnect shaft. The dynamic stability of a proprotor and cantilever wing is calculated, including the engine-transmission-governor model. It is concluded that the rotor behaves much as if windmilling as far as its dynamic behavior is concerned, with some influence of the turboshaft engine inertia and damping. The interconnect shaft has a significant influence on the antisymmetric dynamics of proprotor aircraft. The proprotor aerodynamics model is extended to include reverse flow, and a refinement on the method used to calculate the kinematic pitch-bending coupling of the blade is developed.
Highly dynamic animal contact network and implications on disease transmission
Shi Chen; Brad J. White; Michael W. Sanderson; David E. Amrine; Amiyaal Ilany; Cristina Lanzas
2014-01-01
Contact patterns among hosts are considered as one of the most critical factors contributing to unequal pathogen transmission. Consequently, networks have been widely applied in infectious disease modeling. However most studies assume static network structure due to lack of accurate observation and appropriate analytic tools. In this study we used high temporal and spatial resolution animal position data to construct a high-resolution contact network relevant to infectious disease transmissio...
A mathematical model of Chagas disease transmission
Hidayat, Dayat; Nugraha, Edwin Setiawan; Nuraini, Nuning
2018-03-01
Chagas disease is a parasitic infection caused by protozoan Trypanosoma cruzi which is transmitted to human by insects of the subfamily Triatominae, including Rhodnius prolixus. This disease is a major problem in several countries of Latin America. A mathematical model of Chagas disease with separate vector reservoir and a neighboring human resident is constructed. The basic reproductive ratio is obtained and stability analysis of the equilibria is shown. We also performed sensitivity populations dynamics of infected humans and infected insects based on migration rate, carrying capacity, and infection rate parameters. Our findings showed that the dynamics of the infected human and insect is mostly affected by carrying capacity insect in the settlement.
Final Project Report Load Modeling Transmission Research
Energy Technology Data Exchange (ETDEWEB)
Lesieutre, Bernard [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bravo, Richard [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Yinger, Robert [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Chassin, Dave [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Huang, Henry [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Lu, Ning [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Hiskens, Ian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Venkataramanan, Giri [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2012-03-31
The research presented in this report primarily focuses on improving power system load models to better represent their impact on system behavior. The previous standard load model fails to capture the delayed voltage recovery events that are observed in the Southwest and elsewhere. These events are attributed to stalled air conditioner units after a fault. To gain a better understanding of their role in these events and to guide modeling efforts, typical air conditioner units were testing in laboratories. Using data obtained from these extensive tests, new load models were developed to match air conditioner behavior. An air conditioner model is incorporated in the new WECC composite load model. These models are used in dynamic studies of the West and can impact power transfer limits for California. Unit-level and systemlevel solutions are proposed as potential solutions to the delayed voltage recovery problem.
Characterizing the transmission dynamics and control of ebola virus disease.
Directory of Open Access Journals (Sweden)
Gerardo Chowell
2015-01-01
Full Text Available Carefully calibrated transmission models have the potential to guide public health officials on the nature and scale of the interventions required to control epidemics. In the context of the ongoing Ebola virus disease (EVD epidemic in Liberia, Drake and colleagues, in this issue of PLOS Biology, employed an elegant modeling approach to capture the distributions of the number of secondary cases that arise in the community and health care settings in the context of changing population behaviors and increasing hospital capacity. Their findings underscore the role of increasing the rate of safe burials and the fractions of infectious individuals who seek hospitalization together with hospital capacity to achieve epidemic control. However, further modeling efforts of EVD transmission and control in West Africa should utilize the spatial-temporal patterns of spread in the region by incorporating spatial heterogeneity in the transmission process. Detailed datasets are urgently needed to characterize temporal changes in population behaviors, contact networks at different spatial scales, population mobility patterns, adherence to infection control measures in hospital settings, and hospitalization and reporting rates.
Models for Dynamic Applications
DEFF Research Database (Denmark)
Sales-Cruz, Mauricio; Morales Rodriguez, Ricardo; Heitzig, Martina
2011-01-01
This chapter covers aspects of the dynamic modelling and simulation of several complex operations that include a controlled blending tank, a direct methanol fuel cell that incorporates a multiscale model, a fluidised bed reactor, a standard chemical reactor and finally a polymerisation reactor...... be applied to formulate, analyse and solve these dynamic problems and how in the case of the fuel cell problem the model consists of coupledmeso and micro scale models. It is shown how data flows are handled between the models and how the solution is obtained within the modelling environment....
Brisson, Marc; Bénard, Élodie; Drolet, Mélanie; Bogaards, Johannes A; Baussano, Iacopo; Vänskä, Simopekka; Jit, Mark; Boily, Marie-Claude; Smith, Megan A; Berkhof, Johannes; Canfell, Karen; Chesson, Harrell W; Burger, Emily A; Choi, Yoon H; De Blasio, Birgitte Freiesleben; De Vlas, Sake J; Guzzetta, Giorgio; Hontelez, Jan A C; Horn, Johannes; Jepsen, Martin R; Kim, Jane J; Lazzarato, Fulvio; Matthijsse, Suzette M; Mikolajczyk, Rafael; Pavelyev, Andrew; Pillsbury, Matthew; Shafer, Leigh Anne; Tully, Stephen P; Turner, Hugo C; Usher, Cara; Walsh, Cathal
2016-01-01
Modelling studies have been widely used to inform human papillomavirus (HPV) vaccination policy decisions; however, many models exist and it is not known whether they produce consistent predictions of population-level effectiveness and herd effects. We did a systematic review and meta-analysis of
Mathematical modeling of diphtheria transmission in Thailand.
Sornbundit, Kan; Triampo, Wannapong; Modchang, Charin
2017-08-01
In this work, a mathematical model for describing diphtheria transmission in Thailand is proposed. Based on the course of diphtheria infection, the population is divided into 8 epidemiological classes, namely, susceptible, symptomatic infectious, asymptomatic infectious, carrier with full natural-acquired immunity, carrier with partial natural-acquired immunity, individual with full vaccine-induced immunity, and individual with partial vaccine-induced immunity. Parameter values in the model were either directly obtained from the literature, estimated from available data, or estimated by means of sensitivity analysis. Numerical solutions show that our model can correctly describe the decreasing trend of diphtheria cases in Thailand during the years 1977-2014. Furthermore, despite Thailand having high DTP vaccine coverage, our model predicts that there will be diphtheria outbreaks after the year 2014 due to waning immunity. Our model also suggests that providing booster doses to some susceptible individuals and those with partial immunity every 10 years is a potential way to inhibit future diphtheria outbreaks. Copyright © 2017 Elsevier Ltd. All rights reserved.
DEFF Research Database (Denmark)
Andreasen, Martin Møller; Meldrum, Andrew
This paper studies whether dynamic term structure models for US nominal bond yields should enforce the zero lower bound by a quadratic policy rate or a shadow rate specification. We address the question by estimating quadratic term structure models (QTSMs) and shadow rate models with at most four...
Pulsed Power for a Dynamic Transmission Electron Microscope
Energy Technology Data Exchange (ETDEWEB)
dehope, w j; browning, n; campbell, g; cook, e; king, w; lagrange, t; reed, b; stuart, b; Shuttlesworth, R; Pyke, B
2009-06-25
Lawrence Livermore National Laboratory (LLNL) has converted a commercial 200kV transmission electron microscope (TEM) into an ultrafast, nanoscale diagnostic tool for material science studies. The resulting Dynamic Transmission Electron Microscope (DTEM) has provided a unique tool for the study of material phase transitions, reaction front analyses, and other studies in the fields of chemistry, materials science, and biology. The TEM's thermionic electron emission source was replaced with a fast photocathode and a laser beam path was provided for ultraviolet surface illumination. The resulting photoelectron beam gives downstream images of 2 and 20 ns exposure times at 100 and 10 nm spatial resolution. A separate laser, used as a pump pulse, is used to heat, ignite, or shock samples while the photocathode electron pulses, carefully time-synchronized with the pump, function as probe in fast transient studies. The device functions in both imaging and diffraction modes. A laser upgrade is underway to make arbitrary cathode pulse trains of variable pulse width of 10-1000 ns. Along with a fast e-beam deflection scheme, a 'movie mode' capability will be added to this unique diagnostic tool. This talk will review conventional electron microscopy and its limitations, discuss the development and capabilities of DTEM, in particularly addressing the prime and pulsed power considerations in the design and fabrication of the DTEM, and conclude with the presentation of a deflector and solid-state pulser design for Movie-Mode DTEM.
Transmission dynamics and changing epidemiology of West Nile virus.
Blitvich, Bradley J
2008-06-01
West Nile virus (WNV) is a flavivirus that is maintained in a bird-mosquito transmission cycle. Humans, horses and other non-avian vertebrates are usually incidental hosts, but evidence is accumulating that this might not always be the case. Historically, WNV has been associated with asymptomatic infections and sporadic disease outbreaks in humans and horses in Africa, Europe, Asia and Australia. However, since 1994, the virus has caused frequent outbreaks of severe neuroinvasive disease in humans and horses in Europe and the Mediterranean Basin. In 1999, WNV underwent a dramatic expansion of its geographic range, and was reported for the first time in the Western Hemisphere during an outbreak of human and equine encephalitis in New York City. The outbreak was accompanied by extensive and unprecedented avian mortality. Since then, WNV has dispersed across the Western Hemisphere and is now found throughout the USA, Canada, Mexico and the Caribbean, and parts of Central and South America. WNV has been responsible for >27,000 human cases, >25,000 equine cases and hundreds of thousands of avian deaths in the USA but, surprisingly, there have been only sparse reports of WNV disease in vertebrates in the Caribbean and Latin America. This review summarizes our current understanding of WNV with particular emphasis on its transmission dynamics and changing epidemiology.
Transmission dynamics and prospects for the elimination of canine rabies.
Directory of Open Access Journals (Sweden)
Katie Hampson
2009-03-01
Full Text Available Rabies has been eliminated from domestic dog populations in Western Europe and North America, but continues to kill many thousands of people throughout Africa and Asia every year. A quantitative understanding of transmission dynamics in domestic dog populations provides critical information to assess whether global elimination of canine rabies is possible. We report extensive observations of individual rabid animals in Tanzania and generate a uniquely detailed analysis of transmission biology, which explains important epidemiological features, including the level of variation in epidemic trajectories. We found that the basic reproductive number for rabies, R0, is very low in our study area in rural Africa (approximately 1.2 and throughout its historic global range (<2. This finding provides strong support for the feasibility of controlling endemic canine rabies by vaccination, even near wildlife areas with large wild carnivore populations. However, we show that rapid turnover of domestic dog populations has been a major obstacle to successful control in developing countries, thus regular pulse vaccinations will be required to maintain population-level immunity between campaigns. Nonetheless our analyses suggest that with sustained, international commitment, global elimination of rabies from domestic dog populations, the most dangerous vector to humans, is a realistic goal.
Pulsed Power for a Dynamic Transmission Electron Microscope
International Nuclear Information System (INIS)
DeHope, W.J.; Browning, N.; Campbell, G.; Cook, E.; King, W.; Lagrange, T.; Reed, B.; Stuart, B.; Shuttlesworth, R.; Pyke, B.
2009-01-01
Lawrence Livermore National Laboratory (LLNL) has converted a commercial 200kV transmission electron microscope (TEM) into an ultrafast, nanoscale diagnostic tool for material science studies. The resulting Dynamic Transmission Electron Microscope (DTEM) has provided a unique tool for the study of material phase transitions, reaction front analyses, and other studies in the fields of chemistry, materials science, and biology. The TEM's thermionic electron emission source was replaced with a fast photocathode and a laser beam path was provided for ultraviolet surface illumination. The resulting photoelectron beam gives downstream images of 2 and 20 ns exposure times at 100 and 10 nm spatial resolution. A separate laser, used as a pump pulse, is used to heat, ignite, or shock samples while the photocathode electron pulses, carefully time-synchronized with the pump, function as probe in fast transient studies. The device functions in both imaging and diffraction modes. A laser upgrade is underway to make arbitrary cathode pulse trains of variable pulse width of 10-1000 ns. Along with a fast e-beam deflection scheme, a 'movie mode' capability will be added to this unique diagnostic tool. This talk will review conventional electron microscopy and its limitations, discuss the development and capabilities of DTEM, in particularly addressing the prime and pulsed power considerations in the design and fabrication of the DTEM, and conclude with the presentation of a deflector and solid-state pulser design for Movie-Mode DTEM
Liao, C-M; You, S-H; Cheng, Y-H
2015-01-01
Influenza poses a significant public health burden worldwide. Understanding how and to what extent people would change their behaviour in response to influenza outbreaks is critical for formulating public health policies. We incorporated the information-theoretic framework into a behaviour-influenza (BI) transmission dynamics system in order to understand the effects of individual behavioural change on influenza epidemics. We showed that information transmission of risk perception played a crucial role in the spread of health-seeking behaviour throughout influenza epidemics. Here a network BI model provides a new approach for understanding the risk perception spread and human behavioural change during disease outbreaks. Our study allows simultaneous consideration of epidemiological, psychological, and social factors as predictors of individual perception rates in behaviour-disease transmission systems. We suggest that a monitoring system with precise information on risk perception should be constructed to effectively promote health behaviours in preparation for emerging disease outbreaks.
Directory of Open Access Journals (Sweden)
Lei Wang
2014-01-01
Full Text Available A dynamic model of gear transmission system of wind turbine is built with consideration of randomness of loads and parameters. The dynamic response of the system is obtained using the theory of random sampling and the Runge-Kutta method. According to rain flow counting principle, the dynamic meshing forces are converted into a series of luffing fatigue load spectra. The amplitude and frequency of the equivalent stress are obtained using equivalent method of Geber quadratic curve. Moreover, the dynamic reliability model of components and system is built according to the theory of probability of cumulative fatigue damage. The system reliability with the random variation of parameters is calculated and the influence of random parameters on dynamic reliability of components is analyzed. In the end, the results of the proposed method are compared with that of Monte Carlo method. This paper can be instrumental in the design of wind turbine gear transmission system with more advantageous dynamic reliability.
International Nuclear Information System (INIS)
Nishimura, Hiroshi.
1993-05-01
Object-Oriented Programming has been used extensively to model the LBL Advanced Light Source 1.5 GeV electron storage ring. This paper is on the present status of the class library construction with emphasis on a dynamic modeling
Bun, M.J.G.; Sarafidis, V.
2013-01-01
This Chapter reviews the recent literature on dynamic panel data models with a short time span and a large cross-section. Throughout the discussion we considerlinear models with additional endogenous covariates. First we give a broad overview of available inference methods placing emphasis on GMM.
Ghanem, Bernard
2013-01-01
This paper proposes the problem of modeling video sequences of dynamic swarms (DSs). We define a DS as a large layout of stochastically repetitive spatial configurations of dynamic objects (swarm elements) whose motions exhibit local spatiotemporal interdependency and stationarity, i.e., the motions are similar in any small spatiotemporal neighborhood. Examples of DS abound in nature, e.g., herds of animals and flocks of birds. To capture the local spatiotemporal properties of the DS, we present a probabilistic model that learns both the spatial layout of swarm elements (based on low-level image segmentation) and their joint dynamics that are modeled as linear transformations. To this end, a spatiotemporal neighborhood is associated with each swarm element, in which local stationarity is enforced both spatially and temporally. We assume that the prior on the swarm dynamics is distributed according to an MRF in both space and time. Embedding this model in a MAP framework, we iterate between learning the spatial layout of the swarm and its dynamics. We learn the swarm transformations using ICM, which iterates between estimating these transformations and updating their distribution in the spatiotemporal neighborhoods. We demonstrate the validity of our method by conducting experiments on real and synthetic video sequences. Real sequences of birds, geese, robot swarms, and pedestrians evaluate the applicability of our model to real world data. © 2012 Elsevier Inc. All rights reserved.
Directory of Open Access Journals (Sweden)
Lindsay M Beck-Johnson
Full Text Available The parasites that cause malaria depend on Anopheles mosquitoes for transmission; because of this, mosquito population dynamics are a key determinant of malaria risk. Development and survival rates of both the Anopheles mosquitoes and the Plasmodium parasites that cause malaria depend on temperature, making this a potential driver of mosquito population dynamics and malaria transmission. We developed a temperature-dependent, stage-structured delayed differential equation model to better understand how climate determines risk. Including the full mosquito life cycle in the model reveals that the mosquito population abundance is more sensitive to temperature than previously thought because it is strongly influenced by the dynamics of the juvenile mosquito stages whose vital rates are also temperature-dependent. Additionally, the model predicts a peak in abundance of mosquitoes old enough to vector malaria at more accurate temperatures than previous models. Our results point to the importance of incorporating detailed vector biology into models for predicting the risk for vector borne diseases.
TRANSMISSION SPECTRA OF THREE-DIMENSIONAL HOT JUPITER MODEL ATMOSPHERES
International Nuclear Information System (INIS)
Fortney, J. J.; Shabram, M.; Showman, A. P.; Lian, Y.; Lewis, N. K.; Freedman, R. S.; Marley, M. S.
2010-01-01
We compute models of the transmission spectra of planets HD 209458b, HD 189733b, and generic hot Jupiters. We examine the effects of temperature, surface gravity, and metallicity for the generic planets as a guide to understanding transmission spectra in general. We find that carbon dioxide absorption at 4.4 and 15 μm is prominent at high metallicity, and is a clear metallicity indicator. For HD 209458b and HD 189733b, we compute spectra for both one-dimensional and three-dimensional model atmospheres and examine the differences between them. The differences are usually small, but can be large if atmospheric temperatures are near important chemical abundance boundaries. The calculations for the three-dimensional atmospheres, and their comparison with data, serve as constraints on these dynamical models that complement the secondary eclipse and light curve data sets. For HD 209458b, even if TiO and VO gases are abundant on the dayside, their abundances can be considerably reduced on the cooler planetary limb. However, given the predicted limb temperatures and TiO abundances, the model's optical opacity is too high. For HD 189733b we find a good match with some infrared data sets and constrain the altitude of a postulated haze layer. For this planet, substantial differences can exist between the transmission spectra of the leading and trailing hemispheres, which are an excellent probe of carbon chemistry. In thermochemical equilibrium, the cooler leading hemisphere is methane-dominated, and the hotter trailing hemisphere is CO-dominated, but these differences may be eliminated by non-equilibrium chemistry due to vertical mixing. It may be possible to constrain the carbon chemistry of this planet, and its spatial variation, with James Webb Space Telescope.
Energy Technology Data Exchange (ETDEWEB)
Salles Filho, Anirio
1988-12-01
An automation methodology for dynamic synthesis of electric power transmission network is presented. The dynamic synthesis problem is formulated by an optimization mathematical model. The use of a Lagrangian Relaxation strategy allows to decompose the dynamic problem in a simpler static subproblems sequence. The developed model goal is to establish options of system expansion that minimize the investments total costs and satisfy the increasing demand in time. The method is tested in transmission networks Brazilian system and the obtained results show the utility of a dynamic synthesis tool to assist in complex task of planing the transmission system expansion.
Mathematical modeling for control zika transmission
Nugraha, Edwin Setiawan; Naiborhu, Janson; Nuraini, Nuning; Ahmadin
2017-11-01
After 70 years since the zika was identified in Uganda, zika is now documented in 62 countries. In general, people infected with this disease do not experience severe conditions, but for pregnant women can cause serious problems because the zika can spread to the fetus. One result, zika can cause abnormalities in the fetal brain called microcephaly. Control and prevention are very important to reduce the spread of this disease. Here, we discussed the problem of optimal control in the model of zika transmission associated with the use of insecticide-treated nets (ITN) and indoor residual spraying (IRS). Using the approach of optimal control theory, we completed the objective function so that the infected population and its control cost are minimum. Numerically using the Forward-Backward Sweep Method, we obtained the control design of ITN and IRS as a function of time. The results show that the use of both simultaneously is more effective in reducing the population of infection than the use of ITN alone or the IRS alone.
Schoeftner, J.; Ebner, W.
2017-12-01
Automated and manual transmissions are the main link between engine and powertrain. The technical term when the transmission provides the desired torque during all possible driving conditions is denoted as powertrain matching. Recent developments in the last years show that double-clutch-transmissions (DCTs) are a reasonable compromise in terms of production costs, shifting quality, drivability and fuel efficiency. They have several advantages compared to other automatic transmissions (AT). Most DCTs nowadays consist of a hydraulic actuation control unit, which controls the clutches of the gearbox in order to induce a desired drivetrain torque into the driveline. The main functions of hydraulic systems are manifold: they initiate gear shifts, they provide sufficient oil for lubrication and they control the shift quality by suitably providing a desired oil flow or pressure for the clutch actuation. In this paper, a mathematical model of a passenger car equipped with a DCT is presented. The objective of this contribution is to get an increased understanding for the dynamics of the hydraulic circuit and its coupling to the vehicle drivetrain. The simulation model consists of a hydraulic and a mechanical domain: the hydraulic actuation circuit is described by nonlinear differential equations and includes the dynamics of the line pressure and the proportional valve, as well as the influence of the pressure reducing valve, pipe resistances and accumulator dynamics. The drivetrain with its gear ratios, moments of inertia, torsional stiffness of the rotating shafts and a simple longitudinal vehicle model represent the mechanical domain. The link between hydraulic and mechanical domain is given by the clutch, which combines hydraulic equations and Newton's laws. The presented mathematical model may not only be used as a simulation model for developing the transmission control software, it may also serve as a virtual layout for the design process phase. At the end of this
Multi-scale modelling of supercapacitors: From molecular simulations to a transmission line model
Pean, C.; Rotenberg, B.; Simon, P.; Salanne, M.
2016-09-01
We perform molecular dynamics simulations of a typical nanoporous-carbon based supercapacitor. The organic electrolyte consists in 1-ethyl-3-methylimidazolium and hexafluorophosphate ions dissolved in acetonitrile. We simulate systems at equilibrium, for various applied voltages. This allows us to determine the relevant thermodynamic (capacitance) and transport (in-pore resistivities) properties. These quantities are then injected in a transmission line model for testing its ability to predict the charging properties of the device. The results from this macroscopic model are in good agreement with non-equilibrium molecular dynamics simulations, which validates its use for interpreting electrochemical impedance experiments.
Lumped parametric model of the human ear for sound transmission.
Feng, Bin; Gan, Rong Z
2004-09-01
A lumped parametric model of the human auditoria peripherals consisting of six masses suspended with six springs and ten dashpots was proposed. This model will provide the quantitative basis for the construction of a physical model of the human middle ear. The lumped model parameters were first identified using published anatomical data, and then determined through a parameter optimization process. The transfer function of the middle ear obtained from human temporal bone experiments with laser Doppler interferometers was used for creating the target function during the optimization process. It was found that, among 14 spring and dashpot parameters, there were five parameters which had pronounced effects on the dynamic behaviors of the model. The detailed discussion on the sensitivity of those parameters was provided with appropriate applications for sound transmission in the ear. We expect that the methods for characterizing the lumped model of the human ear and the model parameters will be useful for theoretical modeling of the ear function and construction of the ear physical model.
Photocathode Optimization for a Dynamic Transmission Electron Microscope: Final Report
Energy Technology Data Exchange (ETDEWEB)
Ellis, P; Flom, Z; Heinselman, K; Nguyen, T; Tung, S; Haskell, R; Reed, B W; LaGrange, T
2011-08-04
The Dynamic Transmission Electron Microscope (DTEM) team at Harvey Mudd College has been sponsored by LLNL to design and build a test setup for optimizing the performance of the DTEM's electron source. Unlike a traditional TEM, the DTEM achieves much faster exposure times by using photoemission from a photocathode to produce electrons for imaging. The DTEM team's work is motivated by the need to improve the coherence and current density of the electron cloud produced by the electron gun in order to increase the image resolution and contrast achievable by DTEM. The photoemission test setup is nearly complete and the team will soon complete baseline tests of electron gun performance. The photoemission laser and high voltage power supply have been repaired; the optics path for relaying the laser to the photocathode has been finalized, assembled, and aligned; the internal setup of the vacuum chamber has been finalized and mostly implemented; and system control, synchronization, and data acquisition has been implemented in LabVIEW. Immediate future work includes determining a consistent alignment procedure to place the laser waist on the photocathode, and taking baseline performance measurements of the tantalum photocathode. Future research will examine the performance of the electron gun as a function of the photoemission laser profile, the photocathode material, and the geometry and voltages of the accelerating and focusing components in the electron gun. This report presents the team's progress and outlines the work that remains.
Molecular dynamics of tert-butanol studied by neutron transmission
International Nuclear Information System (INIS)
Amaral, L.Q.; Fulfaro, R.; Vinhas, L.A.
1974-01-01
Neutron transmission of the globular compound tert-butanol (CH 3 ) 3 COH have been measured in the temperature interval O 0 C to 40 0 C for 6.13 A neutrons and in the neutron wavelength range 4A to 7.5A in the liquid and solid states. Results show that the cross-section difference at the state transition in 24 0 C is 13%, while it is only approximately 1% at the first order phase transition in 14 0 C. Evidence of existence of third crystalline phase with the lowest cross-section has been found. The barrier to interval methyl rotation in the solid states is estimated as (3.=+ - 0.5) Kcal/mol and does change much over the phase and state transitions. The observed dynamical changes must be due to movements of the whole molecule and evidence that tert-butanol is not in the strict sense a plastic crystal. Correlation with heat capacity results is discussed
Malafeyev, O. A.; Nemnyugin, S. A.; Rylow, D.; Kolpak, E. P.; Awasthi, Achal
2017-07-01
The corruption dynamics is analyzed by means of the lattice model which is similar to the three-dimensional Ising model. Agents placed at nodes of the corrupt network periodically choose to perfom or not to perform the act of corruption at gain or loss while making decisions based on the process history. The gain value and its dynamics are defined by means of the Markov stochastic process modelling with parameters established in accordance with the influence of external and individual factors on the agent's gain. The model is formulated algorithmically and is studied by means of the computer simulation. Numerical results are obtained which demonstrate asymptotic behaviour of the corruption network under various conditions.
Energy Technology Data Exchange (ETDEWEB)
Kempton, Eliza M.-R. [Department of Physics, Grinnell College, Grinnell, IA 50112 (United States); Perna, Rosalba [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States); Heng, Kevin, E-mail: kemptone@grinnell.edu [University of Bern, Center for Space and Habitability, Sidlerstrasse 5, CH-3012 Bern (Switzerland)
2014-11-01
We present high resolution transmission spectra of giant planet atmospheres from a coupled three-dimensional (3D) atmospheric dynamics and transmission spectrum model that includes Doppler shifts which arise from winds and planetary motion. We model Jovian planets covering more than two orders of magnitude in incident flux, corresponding to planets with 0.9-55 day orbital periods around solar-type stars. The results of our 3D dynamical models reveal certain aspects of high resolution transmission spectra that are not present in simple one-dimensional (1D) models. We find that the hottest planets experience strong substellar to anti-stellar (SSAS) winds, resulting in transmission spectra with net blueshifts of up to 3 km s{sup –1}, whereas less irradiated planets show almost no net Doppler shifts. We find only minor differences between transmission spectra for atmospheres with temperature inversions and those without. Compared to 1D models, peak line strengths are significantly reduced for the hottest atmospheres owing to Doppler broadening from a combination of rotation (which is faster for close-in planets under the assumption of tidal locking) and atmospheric winds. Finally, high resolution transmission spectra may be useful in studying the atmospheres of exoplanets with optically thick clouds since line cores for very strong transitions should remain optically thick to very high altitude. High resolution transmission spectra are an excellent observational test for the validity of 3D atmospheric dynamics models, because they provide a direct probe of wind structures and heat circulation. Ground-based exoplanet spectroscopy is currently on the verge of being able to verify some of our modeling predictions, most notably the dependence of SSAS winds on insolation. We caution that interpretation of high resolution transmission spectra based on 1D atmospheric models may be inadequate, as 3D atmospheric motions can produce a noticeable effect on the absorption
Directory of Open Access Journals (Sweden)
Loktev Aleksey Alekseevich
2013-01-01
Full Text Available The authors present their findings associated with their modeling of a dynamic load damper. According to the authors, the damper is to be installed onto a structure or its element that may be exposed to impact, vibration or any other dynamic loading. The damper is composed of paralleled or consecutively connected viscous and elastic elements. The authors study the influence of viscosity and elasticity parameters of the damper produced onto the regular displacement of points of the structure to be protected and onto the regular acceleration transmitted immediately from the damper to the elements positioned below it.
Zai, Wenjiao; Wang, Bo; Liu, Jichun; Shi, Haobo; Zeng, Pingliang
2018-02-01
The investment decision model of trans-regional transmission network in the context of Global Energy Internet was studied in this paper. The key factors affecting the trans-regional transmission network investment income: the income tax rate, the loan interest rate, the expected return on investment of the investment subject, the per capita GDP and so on were considered in the transmission network investment income model. First, according to the principle of system dynamics, the causality diagram of key factors was constructed. Then, the dynamic model of transmission investment decision was established. A case study of the power transmission network between China and Mongolia, through the simulation of the system dynamic model, the influence of the above key factors on the investment returns was analyzed, and the feasibility and effectiveness of the model was proved.
Transmission dynamics of the recently-identified BYD virus causing duck egg-drop syndrome.
Directory of Open Access Journals (Sweden)
Naveen K Vaidya
Full Text Available Baiyangdian (BYD virus is a recently-identified mosquito-borne flavivirus that causes severe disease in ducks, with extremely rapid transmission, up to 15% mortality within 10 days and 90% reduction in egg production on duck farms within 5 days of infection. Because of the zoonotic nature of flaviviruses, the characterization of BYD virus and its epidemiology are important public health concerns. Here, we develop a mathematical model for the transmission dynamics of this novel virus. We validate the model against BYD outbreak data collected from duck farms in Southeast China, as well as experimental data obtained from an animal facility. Based on our model, the basic reproductive number of BYD virus is high (R(0 = 21 indicating that this virus is highly transmissible, consistent with the dramatic epidemiology observed in BYDV-affected duck farms. Our results indicate that younger ducks are more vulnerable to BYD disease and that ducks infected with BYD virus reduce egg production (to about 33% on average for about 3 days post-infection; after 3 days infected ducks are no longer able to produce eggs. Using our model, we predict that control measures which reduce contact between mosquitoes and ducks such as mosquito nets are more effective than insecticides.
Progress and monitoring system on compression and transmission technologies of dynamic image
International Nuclear Information System (INIS)
Kobayashi, Hiroyuki; Saijo, Nobuyuki; Nakajo, Ken
2001-01-01
The Toshiba Corporation developed a real-time dynamic image transmission matched with quality of transmission circuit by using MPEG-4 which was recent international standard system for the dynamic image coding system. Concretely, this system made possible on real-time dynamic image transmission even at transmission on wireless circuit such as portable telephone, PHS, wireless LAN, and so on, at viewpoint of the mobile communication. And, by using the wireless circuit, it could be built without any limit of transmission cable, to realize its layout-free establishment. In addition, this system uses only image for communication without using voice, and some devices were carried out to upgrade image and frame speed as possible. Here were described on outlines of transmission system and principle of detection MPEG-4, and function and application of monitoring system using this system. (G.K.)
Tornado risk model for transmission line design
CSIR Research Space (South Africa)
Milford, RV
1997-11-01
Full Text Available is in combination with ice loading. The wind load used in most codes of practice and design recommendations for transmission line design have until recently been based almost exclusively on large-scale wind storms, which may include severe storms such as hurricanes...
Dynamic wake meandering modeling
Energy Technology Data Exchange (ETDEWEB)
Larsen, Gunner C.; Aagaard Madsen, H.; Bingoel, F. (and others)
2007-06-15
We present a consistent, physically based theory for the wake meandering phenomenon, which we consider of crucial importance for the overall description of wind turbine loadings in wind farms. In its present version the model is confined to single wake situations. The model philosophy does, however, have the potential to include also mutual wake interaction phenomenons. The basic conjecture behind the dynamic wake meandering model is that wake transportation in the atmospheric boundary layer is driven by the large scale lateral- and vertical turbulence components. Based on this conjecture a stochastic model of the downstream wake meandering is formulated. In addition to the kinematic formulation of the dynamics of the 'meandering frame of reference', models characterizing the mean wake deficit as well as the added wake turbulence, described in the meandering frame of reference, are an integrated part the model complex. For design applications, the computational efficiency of wake deficit prediction is a key issue. Two computationally low cost models are developed for this purpose. The character of the added wake turbulence, generated by the up-stream turbine in the form of shed and trailed vorticity, has been approached by analytical as well as by numerical studies. The dynamic wake meandering philosophy has been verified by comparing model predictions with extensive full-scale measurements. These comparisons have demonstrated good agreement, both qualitatively and quantitatively, concerning both flow characteristics and turbine load characteristics. Contrary to previous attempts to model wake loading, the dynamic wake meandering approach opens for a unifying description in the sense that turbine power and load aspects can be treated simultaneously. This capability is a direct and attractive consequence of the model being based on the underlying physical process, and it potentially opens for optimization of wind farm topology, of wind farm operation as
Modeling of spectral atmosphere transmission for infrared radiation
International Nuclear Information System (INIS)
Wiecek, B.; Olbrycht, R.
2009-01-01
IR radiation transmission of the atmosphere is an important factor during the thermovision remote sensing and measurement. Transmission coefficient of the atmosphere depends on its content and it is attenuated mainly due to the vapor concentration. Every calibrated thermal camera should be equipped with the digital system which implements the transmission model of the atmosphere. The model presented in this work is based on Beer and Bouguer laws. The proposed simplified model of transmission atmosphere is suitable for implementation in the thermal cameras. A simple digital controller of the camera can calculate the transmission coefficient and correct the temperature measurement. The model takes in account both scattering and absorption due the quantum effects when the photons are interacting with the molecules. (author)
International Nuclear Information System (INIS)
Colanero, K.; Chu, M.-C.
2002-01-01
We study a dynamical chiral bag model, in which massless fermions are confined within an impenetrable but movable bag coupled to meson fields. The self-consistent motion of the bag is obtained by solving the equations of motion exactly assuming spherical symmetry. When the bag interacts with an external meson wave we find three different kinds of resonances: fermionic, geometric, and σ resonances. We discuss the phenomenological implications of our results
Model for macroevolutionary dynamics.
Maruvka, Yosef E; Shnerb, Nadav M; Kessler, David A; Ricklefs, Robert E
2013-07-02
The highly skewed distribution of species among genera, although challenging to macroevolutionists, provides an opportunity to understand the dynamics of diversification, including species formation, extinction, and morphological evolution. Early models were based on either the work by Yule [Yule GU (1925) Philos Trans R Soc Lond B Biol Sci 213:21-87], which neglects extinction, or a simple birth-death (speciation-extinction) process. Here, we extend the more recent development of a generic, neutral speciation-extinction (of species)-origination (of genera; SEO) model for macroevolutionary dynamics of taxon diversification. Simulations show that deviations from the homogeneity assumptions in the model can be detected in species-per-genus distributions. The SEO model fits observed species-per-genus distributions well for class-to-kingdom-sized taxonomic groups. The model's predictions for the appearance times (the time of the first existing species) of the taxonomic groups also approximately match estimates based on molecular inference and fossil records. Unlike estimates based on analyses of phylogenetic reconstruction, fitted extinction rates for large clades are close to speciation rates, consistent with high rates of species turnover and the relatively slow change in diversity observed in the fossil record. Finally, the SEO model generally supports the consistency of generic boundaries based on morphological differences between species and provides a comparator for rates of lineage splitting and morphological evolution.
Littlewood, Kavi J; Ouwens, Mario J N M; Sauboin, Christophe; Tehard, Bertrand; Alain, Sophie; Denis, François
2015-04-01
Each year in France, varicella and zoster affect large numbers of children and adults, resulting in medical visits, hospitalizations for varicella- and zoster-related complications, and societal costs. Disease prevention by varicella vaccination is feasible, wherein a plausible option involves replacing the combined measles, mumps, and rubella (MMR) vaccine with the combined MMR and varicella (MMRV) vaccine. This study aimed to: (1) assess the cost-effectiveness of adding routine varicella vaccination through MMRV, using different vaccination strategies in France; and (2) address key uncertainties, such as the economic consequences of breakthrough varicella cases, the waning of vaccine-conferred protection, vaccination coverage, and indirect costs. Based on the outputs of a dynamic transmission model that used data on epidemiology and costs from France, a cost-effectiveness model was built. A conservative approach was taken regarding the impact of varicella vaccination on zoster incidence by assuming the validity of the hypothesis of an age-specific boosting of immunity against varicella. The model determined that routine MMRV vaccination is expected to be a cost-effective option, considering a cost-effectiveness threshold of €20,000 per quality-adjusted life-year saved; routine vaccination was cost-saving from the societal perspective. Results were driven by a large decrease in varicella incidence despite a temporary initial increase in the number of zoster cases due to the assumption of exogenous boosting. In the scenario analyses, despite moderate changes in assumptions about incidence and costs, varicella vaccination remained a cost-effective option for France. Routine vaccination with MMRV was associated with high gains in quality-adjusted life-years, substantial reduction in the occurrences of varicella- and zoster-related complications, and few deaths due to varicella. Routine MMRV vaccination is also expected to provide reductions in costs related to
International Nuclear Information System (INIS)
McFadden, J.H.; Paulsen, M.P.; Gose, G.C.
1981-01-01
Thermal-hydraulic codes in general use for system calculations are based on extensive analyses of loss-of-coolant accidents following the postulated rupture of a large coolant pipe. In this study, time-dependent equation for the slip velocity in a two-phase flow condition has been incorporated into the RETRAN-02 computer code. This model addition was undertaken to remove a limitation in RETRAN-01 associated with the homogeneous equilibrium mixture model. The dynamic slip equation was derived from a set of two-fluid conservation equations. 18 refs
Glaese, John R.; Tobbe, Patrick A.
1986-01-01
The Space Station Mechanism Test Bed consists of a hydraulically driven, computer controlled six degree of freedom (DOF) motion system with which docking, berthing, and other mechanisms can be evaluated. Measured contact forces and moments are provided to the simulation host computer to enable representation of orbital contact dynamics. This report describes the development of a generalized math model which represents the relative motion between two rigid orbiting vehicles. The model allows motion in six DOF for each body, with no vehicle size limitation. The rotational and translational equations of motion are derived. The method used to transform the forces and moments from the sensor location to the vehicles' centers of mass is also explained. Two math models of docking mechanisms, a simple translational spring and the Remote Manipulator System end effector, are presented along with simulation results. The translational spring model is used in an attempt to verify the simulation with compensated hardware in the loop results.
Grounding modelling for transient overvoltage simulation in electric power transmission
International Nuclear Information System (INIS)
Moreno O, German; Valencia V, Jaime A; Villada, Fernando
1992-01-01
Grounding plays an important role in transmission line outages and consequently on electric energy transmission quality indexes. Fundamentals of an accurate modelling for transient behaviour analysis, particularly for the response of transmission lines to lightning, are presented. Also, a method to take into account the electromagnetic propagation guided by the grounding electrodes and finally to assess the grounding impedance in order to simulate the transmission line behaviour under lightning is presented. Analysis of impedance behaviour for diverse configurations and simulation results of over voltages on a real 220 kV line are presented to illustrate the capabilities of the method and of the computational program developed
A unified modeling and control design for precision transmission system with friction and backlash
Directory of Open Access Journals (Sweden)
Xiulan Bao
2016-05-01
Full Text Available The structural flexibility, nonlinear friction, and backlash are the major factors limiting the control performance of precision transmission systems. If uncompensated, these factors compromise the positioning and tracking accuracy of precision transmission systems and even cause limit cycles and oscillation. In this article, a framework for integrated design from dynamic modeling to controller design is proposed. A multi-state dynamic model is presented, which can unify the modeling for a multi-state, discontinuous system including the motor state, the motion state, the mechanical contact state, and the friction state. Then, a control design method related to the dynamic modeling using perturbation separation of the model parameters is presented. Using the proposed modeling method, a continuous dynamic model is established to include all different partition models. The model comprehensively describes the mechanical and electrical characteristics of the precision transmission system. A robust controller is designed using the proposed control method. Experimental results demonstrate that the proposed modeling method is accurate and the proposed control method significantly improves accuracy and robustness of the controller compared to traditional control methods.
Oraby, Tamer; Vasilyeva, Olga; Krewski, Daniel; Lutscher, Frithjof
2014-01-07
Behavior and habitat of wildlife animals change seasonally according to environmental conditions. Mathematical models need to represent this seasonality to be able to make realistic predictions about the future of a population and the effectiveness of human interventions. Managing and modeling disease in wild animal populations requires particular care in that disease transmission dynamics is a critical consideration in the etiology of both human and animal diseases, with different transmission paradigms requiring different disease risk management strategies. Since transmission of infectious diseases among wildlife depends strongly on social behavior, mechanisms of disease transmission could also change seasonally. A specific consideration in this regard confronted by modellers is whether the contact rate between individuals is density-dependent or frequency-dependent. We argue that seasonal behavior changes could lead to a seasonal shift between density and frequency dependence. This hypothesis is explored in the case of chronic wasting disease (CWD), a fatal disease that affects deer, elk and moose in many areas of North America. Specifically, we introduce a strategic CWD risk model based on direct disease transmission that accounts for the seasonal change in the transmission dynamics and habitats occupied, guided by information derived from cervid ecology. The model is composed of summer and winter susceptible-infected (SI) equations, with frequency-dependent and density-dependent transmission dynamics, respectively. The model includes impulsive birth events with density-dependent birth rate. We determine the basic reproduction number as a weighted average of two seasonal reproduction numbers. We parameterize the model from data derived from the scientific literature on CWD and deer ecology, and conduct global and local sensitivity analyses of the basic reproduction number. We explore the effectiveness of different culling strategies for the management of CWD
Method of transmission of dynamic multibit digital images from micro-unmanned aerial vehicles
Petrov, E. P.; Kharina, N. L.
2018-01-01
In connection with successful usage of nanotechnologies in remote sensing great attention is paid to the systems in micro-unmanned aerial vehicles (MUAVs) capable to provide high spatial resolution of dynamic multibit digital images (MDI). Limited energy resources on board the MUAV do not allow transferring a large amount of video information in the shortest possible time. It keeps back the broad development of MUAV. The search for methods to shorten the transmission time of dynamic MDIs from MUAV over the radio channel leads to the methods of MDI compression without computational operations onboard the MUAV. The known compression codecs of video information can not be applied because of the limited energy resources. In this paper we propose a method for reducing the transmission time of dynamic MDIs without computational operations and distortions onboard the MUAV. To develop the method a mathematical apparatus of the theory of conditional Markov processes with discrete arguments was used. On its basis a mathematical model for the transformation of the MDI represented by binary images (BI) in the MDI, consisting of groups of neighboring BIs (GBI) transmitted by multiphase (MP) signals, is constructed. The algorithm for multidimensional nonlinear filtering of MP signals is synthesized, realizing the statistical redundancy of the MDI to compensate for the noise stability losses caused by the use of MP signals.
Analysis of main dynamic parameters of split power transmission
Directory of Open Access Journals (Sweden)
A. Janulevičius
2008-06-01
Full Text Available The review carried out had shown one basic approach of split power transmission to the organization of drive which is applied to stepless transmissions of tractors and parallel hybrid cars. In the split power transmission the power split device uses a planetary gear. Tractor engine power in the split power transmission is transmitted to the drive shaft via a mechanical and hydraulic path. The theoretical analysis of main parameters of the split power transmission of the tractor is presented. The angular velocity of sun and coronary gears of the differential set is estimated by solution of the system of equations in which one equation is made for planetary differential gear, and another – for hydrostatic drive. The analysis of the transmission gear-ratio dependencies on the ratio of hydraulic machines capacities is carried out. Dependence of the variation of angular velocity of the coronary and the sun gears on the ground speed of the tractor is presented. Dependence of sum shaft torque and its constituents, carried by mechanical and hydraulic lines, on sum shaft angular velocity and ground speed of tractor and engine speed is also presented.
Directory of Open Access Journals (Sweden)
Wang Jungang
2017-01-01
Full Text Available Dynamic behavior of planetary gear’s tooth contact surface in the different location can better conform operation condition comparing to the general gear pair. Nonlinear finite element algorithm was derived according to the basic control equation of contact dynamics. A finite element model of planetary gear transmission in wind power increasing gearbox was proposed considering different meshing locations based on nonlinear finite element solution. The characteristics of stress distribution at different meshing positions were analyzed. A simulation of the meshing process was conducted using finite element analysis. It was shown that node stresses of external meshing planetary gear varied significantly at different position. The analysis provides some useful insights into the performance of planetary gear’s tooth contact surface.
A Data Transmission Algorithm Based on Dynamic Grid Division for Coal Goaf Temperature Monitoring
Directory of Open Access Journals (Sweden)
Qingsong Hu
2014-01-01
Full Text Available WSN (wireless sensor network is a perfect tool of temperature monitoring in coal goaf. Based on the three-zone theory of goaf, the GtmWSN model is proposed, and its dynamic features are analyzed. Accordingly, a data transmission scheme, named DTDGD, is worked out. Firstly, sink nodes conduct dynamic grid division on the GtmWSN according to virtual semicircle. Secondly, each node will confirm to which grid it belongs based on grid number. Finally, data will be delivered to sink nodes with greedy forward and hole avoidance. Simulation results and field data showed that the GtmWSN and DTDGD satisfied the lifetime need of goaf temperature monitoring.
Modeling the effect of comprehensive interventions on Ebola virus transmission
Shen, Mingwang; Xiao, Yanni; Rong, Libin
2015-10-01
Since the re-emergence of Ebola in West Africa in 2014, comprehensive and stringent interventions have been implemented to decelerate the spread of the disease. The effectiveness of interventions still remains unclear. In this paper, we develop an epidemiological model that includes various controlling measures to systematically evaluate their effects on the disease transmission dynamics. By fitting the model to reported cumulative cases and deaths in Guinea, Sierra Leone and Liberia until March 22, 2015, we estimate the basic reproduction number in these countries as 1.2552, 1.6093 and 1.7994, respectively. Model analysis shows that there exists a threshold of the effectiveness of isolation, below which increasing the fraction of latent individuals diagnosed prior to symptoms onset or shortening the duration between symptoms onset and isolation may lead to more Ebola infection. This challenges an existing view. Media coverage plays a substantial role in reducing the final epidemic size. The response to reported cumulative infected cases and deaths may have a different effect on the epidemic spread in different countries. Among all the interventions, we find that shortening the duration between death and burial and improving the effectiveness of isolation are two effective interventions for controlling the outbreak of Ebola virus infection.
Raabe, K.; Arnold, I.; Kool, C.J.M.
This paper presents a dynamic investment model that explains differences in the sensitivity of small- and large-sized firms to changes in the money market interest rate. In contrast to existing studies on the firm size effects of monetary policy, the importance of firms as monetary transmission
Analysis of a malaria model with mosquito-dependent transmission ...
Indian Academy of Sciences (India)
model for the spread of malaria in human and mosquito population. ... tures, high humidity and water bodies allow mosquito and parasites to reproduce. The ... understand the main parameters in the transmission of the disease and to develop ...
DEFF Research Database (Denmark)
Borregaard, Michael K.; Matthews, Thomas J.; Whittaker, Robert James
2016-01-01
Aim: Island biogeography focuses on understanding the processes that underlie a set of well-described patterns on islands, but it lacks a unified theoretical framework for integrating these processes. The recently proposed general dynamic model (GDM) of oceanic island biogeography offers a step...... towards this goal. Here, we present an analysis of causality within the GDM and investigate its potential for the further development of island biogeographical theory. Further, we extend the GDM to include subduction-based island arcs and continental fragment islands. Location: A conceptual analysis...... of evolutionary processes in simulations derived from the mechanistic assumptions of the GDM corresponded broadly to those initially suggested, with the exception of trends in extinction rates. Expanding the model to incorporate different scenarios of island ontogeny and isolation revealed a sensitivity...
Gerardin, Jaline; Bever, Caitlin A; Bridenbecker, Daniel; Hamainza, Busiku; Silumbe, Kafula; Miller, John M; Eisele, Thomas P; Eckhoff, Philip A; Wenger, Edward A
2017-06-12
Reactive case detection could be a powerful tool in malaria elimination, as it selectively targets transmission pockets. However, field operations have yet to demonstrate under which conditions, if any, reactive case detection is best poised to push a region to elimination. This study uses mathematical modelling to assess how baseline transmission intensity and local interconnectedness affect the impact of reactive activities in the context of other possible intervention packages. Communities in Southern Province, Zambia, where elimination operations are currently underway, were used as representatives of three archetypes of malaria transmission: low-transmission, high household density; high-transmission, low household density; and high-transmission, high household density. Transmission at the spatially-connected household level was simulated with a dynamical model of malaria transmission, and local variation in vectorial capacity and intervention coverage were parameterized according to data collected from the area. Various potential intervention packages were imposed on each of the archetypical settings and the resulting likelihoods of elimination by the end of 2020 were compared. Simulations predict that success of elimination campaigns in both low- and high-transmission areas is strongly dependent on stemming the flow of imported infections, underscoring the need for regional-scale strategies capable of reducing transmission concurrently across many connected areas. In historically low-transmission areas, treatment of clinical malaria should form the cornerstone of elimination operations, as most malaria infections in these areas are symptomatic and onward transmission would be mitigated through health system strengthening; reactive case detection has minimal impact in these settings. In historically high-transmission areas, vector control and case management are crucial for limiting outbreak size, and the asymptomatic reservoir must be addressed through
Dynamics of a scrapie outbreak in a flock of Romanov sheep-estimation of transmission parameters
Hagenaars, T.H.J.; Donelly, C.A.; Ferguson, N.M.; Anderson, R.M.
2003-01-01
Knowledge of epidemiological mechanisms and parameters underlying scrapie transmission in sheep flocks remains very limited at present. Here we introduce a method for fitting stochastic transmission models to outbreak data to estimate bounds on key transmission parameters. We apply this method to
Transmission Dinamics Model Of Dengue Fever
Debora; Rendy; Rahmi
2018-01-01
Dengue fever is an endemic disease that is transmitted through the Aedes aegypti mosquito vector. The disease is present in more than 100 countries in America, Africa, and Asia, especially tropical countries. Differential equations can be used to represent the spread of dengue virus occurring in time intervals and model in the form of mathematical models. The mathematical model in this study tries to represent the spread of dengue fever based on the data obtained and the assumptions used. The mathematical model used is a mathematical model consisting of Susceptible (S), Infected (I), Viruses (V) subpopulations. The SIV mathematical model is then analyzed to see the solution behaviour of the system.
Transmission dynamics of lumpy skin disease in Ethiopia
Molla, W.; Frankena, Klaas; Jong, de Mart
2017-01-01
Lumpy skin disease (LSD) is a severe disease of cattle caused by a Capripoxvirus and often caused epidemics in Ethiopia and many other countries. This study was undertaken to quantify the transmission between animals and to estimate the infection reproduction ratio in a predominantly mixed
Inflation Dynamics and the Cost Channel of Monetary Transmission
Chowdhury, I.; Hoffmann, M.; Schabert, A.
2006-01-01
Evidence from vector autoregressions indicates that the impact of interest rate shocks on macroeconomic aggregates can substantially be affected by the so-called cost channel of monetary transmission. In this paper, we apply a structural approach to examine the relevance of the cost channel for
Simulation of Dynamic Behavior of the Flexible Wheel of the Double Harmonic Gear Transmission
Directory of Open Access Journals (Sweden)
Draghiţa Ianici
2014-06-01
Full Text Available The paper presents the construction and functioning of a new type the harmonic gear transmission named double harmonic gear transmission, which can be used in the construction drives of industrial robots. In the second part of this paper is presented the dynamic analysis of the double harmonic gear transmission, which is based on the results of the numerical simulations of the flexible wheel in case of its deformation with a mechanical wave generator with disc cam. Investigation of dynamic behavior of the flexible toothed wheel was performed by using the finite element method in SolidWorks Simulation software.
Campagnoli, Patrizia; Petris, Giovanni
2009-01-01
State space models have gained tremendous popularity in as disparate fields as engineering, economics, genetics and ecology. Introducing general state space models, this book focuses on dynamic linear models, emphasizing their Bayesian analysis. It illustrates the fundamental steps needed to use dynamic linear models in practice, using R package.
GIS and dynamic phenomena modeling
Czech Academy of Sciences Publication Activity Database
Klimešová, Dana
2006-01-01
Roč. 4, č. 4 (2006), s. 11-15 ISSN 0139-570X Institutional research plan: CEZ:AV0Z10750506 Keywords : dynamic modelling * temporal analysis * dynamics evaluation * temporal space Subject RIV: BC - Control Systems Theory
ARMAX, OE and SSIF model predictors for power transmission and ...
African Journals Online (AJOL)
Three mathematical model structures, namely: ARMAX, OE and a SSIF are first formulated followed by the formulation of their respective model predictors for the model identification and prediction of power transmission and distribution within Akure and its environs. A total of 51,350 data samples from the Power Holding ...
International Nuclear Information System (INIS)
Roehling, John D.; Coughlin, Daniel R.; Gibbs, John W.; Baldwin, J. Kevin; Mertens, James C.E.; Campbell, Geoffrey H.; Clarke, Amy J.; McKeown, Joseph T.
2017-01-01
In situ dynamic transmission electron microscope (DTEM) imaging of Al-Si thin-film alloys was performed to investigate rapid solidification behavior. Solidification of alloys with compositions from 1 to 15 atomic percent Si was imaged during pulsed laser melting and subsequent solidification. Solely α-Al solidification was observed in Al-1Si and Al-3Si alloys, and solely kinetically modified eutectic growth was observed in Al-6Si and Al-9Si alloys. A transition in the solidification mode in eutectic and hypereutectic alloys (Al-12Si and Al-15Si) from nucleated α-Al dendrites at lower solidification velocities to planar eutectic growth at higher solidification velocities was observed, departing from trends previously seen in laser-track melting experiments. Comparisons of the growth modes and corresponding velocities are compared with previous solidification models, and implications regarding the models are discussed.
Five challenges for stochastic epidemic models involving global transmission
Directory of Open Access Journals (Sweden)
Tom Britton
2015-03-01
Full Text Available The most basic stochastic epidemic models are those involving global transmission, meaning that infection rates depend only on the type and state of the individuals involved, and not on their location in the population. Simple as they are, there are still several open problems for such models. For example, when will such an epidemic go extinct and with what probability (questions depending on the population being fixed, changing or growing? How can a model be defined explaining the sometimes observed scenario of frequent mid-sized epidemic outbreaks? How can evolution of the infectious agent transmission rates be modelled and fitted to data in a robust way?
International Nuclear Information System (INIS)
Meng Xinzhu; Jiao Jianjun; Chen Lansun
2009-01-01
Since the investigation of impulsive delay differential equations is beginning, the literature on delay epidemic models with pulse vaccination is not extensive. In this paper, we propose a new SEIRS epidemic disease model with two profitless delays and vertical transmission, and analyze the dynamics behaviors of the model under pulse vaccination. Using the discrete dynamical system determined by the stroboscopic map, we obtain a 'infection-free' periodic solution, further, show that the 'infection-free' periodic solution is globally attractive when some parameters of the model are under appropriate conditions. Using a new modeling method, we obtain sufficient condition for the permanence of the epidemic model with pulse vaccination. We show that time delays, pulse vaccination and vertical transmission can bring different effects on the dynamics behaviors of the model by numerical analysis. Our results also show the delays are 'profitless'. In this paper, the main feature is to introduce two discrete time delays, vertical transmission and impulse into SEIRS epidemic model and to give pulse vaccination strategies.
Vrancken, Bram; Rambaut, Andrew; Suchard, Marc A.; Drummond, Alexei; Baele, Guy; Derdelinckx, Inge; Van Wijngaerden, Eric; Vandamme, Anne-Mieke; Van Laethem, Kristel; Lemey, Philippe
2014-01-01
Transmission lies at the interface of human immunodeficiency virus type 1 (HIV-1) evolution within and among hosts and separates distinct selective pressures that impose differences in both the mode of diversification and the tempo of evolution. In the absence of comprehensive direct comparative analyses of the evolutionary processes at different biological scales, our understanding of how fast within-host HIV-1 evolutionary rates translate to lower rates at the between host level remains incomplete. Here, we address this by analyzing pol and env data from a large HIV-1 subtype C transmission chain for which both the timing and the direction is known for most transmission events. To this purpose, we develop a new transmission model in a Bayesian genealogical inference framework and demonstrate how to constrain the viral evolutionary history to be compatible with the transmission history while simultaneously inferring the within-host evolutionary and population dynamics. We show that accommodating a transmission bottleneck affords the best fit our data, but the sparse within-host HIV-1 sampling prevents accurate quantification of the concomitant loss in genetic diversity. We draw inference under the transmission model to estimate HIV-1 evolutionary rates among epidemiologically-related patients and demonstrate that they lie in between fast intra-host rates and lower rates among epidemiologically unrelated individuals infected with HIV subtype C. Using a new molecular clock approach, we quantify and find support for a lower evolutionary rate along branches that accommodate a transmission event or branches that represent the entire backbone of transmitted lineages in our transmission history. Finally, we recover the rate differences at the different biological scales for both synonymous and non-synonymous substitution rates, which is only compatible with the ‘store and retrieve’ hypothesis positing that viruses stored early in latently infected cells
An epidemiological model of virus transmission in salmonid fishes of the Columbia River Basin
Ferguson, Paige F. B.; Breyta, Rachel; Brito, Ilana L.; Kurath, Gael; LaDeau, Shannon L.
2018-01-01
We have developed a dynamic epidemiological model informed by records of viral presence and genotypes to evaluate potential transmission routes maintaining a viral pathogen in economically and culturally important anadromous fish populations. In the Columbia River Basin, infectious hematopoietic necrosis virus (IHNV) causes severe disease, predominantly in juvenile steelhead trout (Oncorhynchus mykiss) and less frequently in Chinook salmon (O. tshawytscha). Mortality events following IHNV infection can be devastating for individual hatchery programs. Despite reports of high local mortality and extensive surveillance efforts, there are questions about how viral transmission is maintained. Modeling this system offers important insights into disease transmission in natural aquatic systems, as well as about the data requirements for generating accurate estimates about transmission routes and infection probabilities. We simulated six scenarios in which testing rates and the relative importance of different transmission routes varied. The simulations demonstrated that the model accurately identified routes of transmission and inferred infection probabilities accurately when there was testing of all cohort-sites. When testing records were incomplete, the model accurately inferred which transmission routes exposed particular cohort-sites but generated biased infection probabilities given exposure. After validating the model and generating guidelines for result interpretation, we applied the model to data from 14 annual cohorts (2000–2013) at 24 focal sites in a sub-region of the Columbia River Basin, the lower Columbia River (LCR), to quantify the relative importance of potential transmission routes in this focal sub-region. We demonstrate that exposure to IHNV via the return migration of adult fish is an important route for maintaining IHNV in the LCR sub-region, and the probability of infection following this exposure was relatively high at 0.16. Although only 1% of
Modeling Influenza Transmission Using Environmental Parameters
Soebiyanto, Radina P.; Kiang, Richard K.
2010-01-01
Influenza is an acute viral respiratory disease that has significant mortality, morbidity and economic burden worldwide. It infects approximately 5-15% of the world population, and causes 250,000 500,000 deaths each year. The role of environments on influenza is often drawn upon the latitude variability of influenza seasonality pattern. In regions with temperate climate, influenza epidemics exhibit clear seasonal pattern that peak during winter months, but it is not as evident in the tropics. Toward this end, we developed mathematical model and forecasting capabilities for influenza in regions characterized by warm climate Hong Kong (China) and Maricopa County (Arizona, USA). The best model for Hong Kong uses Land Surface Temperature (LST), precipitation and relative humidity as its covariates. Whereas for Maricopa County, we found that weekly influenza cases can be best modelled using mean air temperature as its covariates. Our forecasts can further guides public health organizations in targeting influenza prevention and control measures such as vaccination.
Modelling dynamic roughness during floods
Paarlberg, Andries; Dohmen-Janssen, Catarine M.; Hulscher, Suzanne J.M.H.; Termes, A.P.P.
2007-01-01
In this paper, we present a dynamic roughness model to predict water levels during floods. Hysteresis effects of dune development are explicitly included. It is shown that differences between the new dynamic roughness model, and models where the roughness coefficient is calibrated, are most
A universal calculation model for the controlled electric transmission line
International Nuclear Information System (INIS)
Zivzivadze, O.; Zivzivadze, L.
2009-01-01
Difficulties associated with the development of calculation models are analyzed, and the ways of resolution of these problems are given. A version of the equivalent circuit as a six-pole network, the parameters of which do not depend on the angle of shift Θ between the voltage vectors of circuits is offered. The interrelation between the parameters of the equivalent circuit and the transmission constants of the line was determined. A universal calculation model for the controlled electric transmission line was elaborated. The model allows calculating the stationary modes of lines of such classes at any angle of shift Θ between the circuits. (author)
Mathematical model of Zika virus with vertical transmission
Directory of Open Access Journals (Sweden)
F.B. Agusto
2017-05-01
Full Text Available Zika is a flavivirus transmitted to humans through either the bites of infected Aedes mosquitoes or sexual transmission. Zika has been linked to congenital anomalies such as microcephaly. In this paper, we analyze a new system of ordinary differential equations which incorporates human vertical transmission of Zika virus, the birth of babies with microcephaly and asymptomatically infected individuals. The Zika model is locally and globally asymptotically stable when the basic reproduction number is less than unity. Our model shows that asymptomatic individuals amplify the disease burden in the community, and the most important parameters for ZIKV spread are the death rate of mosquitoes, the mosquito biting rate, the mosquito recruitment rate, and the transmission per contact to mosquitoes and to adult humans. Scenario exploration indicates that personal-protection is a more effective control strategy than mosquito-reduction strategy. It also shows that delaying conception reduces the number of microcephaly cases, although this does little to prevent Zika transmission in the broader community. However, by coupling aggressive vector control and personal protection use, it is possible to reduce both microcephaly and Zika transmission. 2000 Mathematics Subject Classifications: 92B05, 93A30, 93C15. Keywords: Zika virus, Vertical transmission, Microcephaly, Stability, Control
Analysis of a Malaria Model with Mosquito-Dependent Transmission ...
Indian Academy of Sciences (India)
In this paper, we discuss an ordinary differential equation mathematical model for the spread of malaria in human and mosquito population. We suppose the human population to act as a reservoir. Both the species follow a logistic population model. The transmission coefficient or the interaction coefficient of humans is ...
Flexible AC transmission systems. Modelling and control
Energy Technology Data Exchange (ETDEWEB)
Zhang, Xiao-Ping [Birmingham Univ. (United Kingdom); Rehtanz, Christian [Technische Univ. Dortmund (Germany); Pal, Bikash [Imperial College, London (United Kingdom)
2012-11-01
This monograph presents advanced modelling, analysis and control techniques of FACTS. These topics reflect the recent research and development of FACTS controllers, and anticipate the future applications of FACTS in power systems. The book covers comprehensively a range of power-system control problems: from steady-state voltage and power flow control, to voltage and reactive power control, to voltage stability control, to small signal stability control using FACTS controllers. The book presents the modelling of the latest FACTS controllers for power flow control, compensation and power quality (IPFC, GUPF, VSC HVDC and M-VSCHVDC, etc.) in power system analysis. The selection is evaluated by the actual and likely future practical relevance of each. The material is derived mainly from the research and industrial development in which the authors have been heavily involved. The book is timely and of great value to power engineering engineers and students of modelling, simulations and control design of FACTS for a broad practical range of power system operation, planning and control problems.
Mathematical model of transmission network static state estimation
Directory of Open Access Journals (Sweden)
Ivanov Aleksandar
2012-01-01
Full Text Available In this paper the characteristics and capabilities of the power transmission network static state estimator are presented. The solving process of the mathematical model containing the measurement errors and their processing is developed. To evaluate difference between the general model of state estimation and the fast decoupled state estimation model, the both models are applied to an example, and so derived results are compared.
Rigorous theoretical derivation of lumped models to transmission line systems
International Nuclear Information System (INIS)
Zhao Jixiang
2012-01-01
By virtue of the negative electric parameter concept, i.e. negative lumped resistance, inductance, conductance and capacitance (N-RLGC), the lumped equivalent models of transmission line systems, including the circuit model, two-port π-network and T-network, are given. We start from the N-segment-ladder-like equivalent networks composed distributed parameters, and achieve the input impedance in the form of a continued fraction. Utilizing the continued fraction theory, the expressions of input impedance are obtained under three kinds of extreme cases, i.e. the load impedances are equal to zero, infinity and characteristic impedance, respectively. When the number of segment N is limited to infinity, they are transformed to lumped elements. Comparison between the distributed model and lumped model of transmission lines, the expression of tanh γd, which is the key term in the transmission line equations, are obtained by RLGC, furthermore, according to input admittance, admittance matrix and ABCD matrix of transmission lines, the lumped equivalent circuit models, π-networks and T-networks have been given. The models are verified in the frequency and time domain, respectively, showing that the models are accurate and efficient. (semiconductor integrated circuits)
Dynamic simulation of hvdc transmission systems on digital computers
Energy Technology Data Exchange (ETDEWEB)
Hingorani, N G; Hay, J L; Crosbie, R E
1966-05-01
A digital computer technique is based on the fact that the operation of an hvdc converter consists of similar consecutive processes, each process having features which are common to all processes. Each bridge converter of an hvdc system is represented by a central process, and repetitive use of the latter simulates continuous converter operation. This technique may be employed to obtain the waveforms of transient or steady state voltages and currents anywhere in the dc system. To illustrate the method, an hvdc link is considered; the link which connects two independent ac systems conprises two converters with their control systems, and a dc transmission line. As an example, the transient behavior of the system is examined following changes in the current settings of the control system.
Comparison of Transmission Line Methods for Surface Acoustic Wave Modeling
Wilson, William; Atkinson, Gary
2009-01-01
Surface Acoustic Wave (SAW) technology is low cost, rugged, lightweight, extremely low power and can be used to develop passive wireless sensors. For these reasons, NASA is investigating the use of SAW technology for Integrated Vehicle Health Monitoring (IVHM) of aerospace structures. To facilitate rapid prototyping of passive SAW sensors for aerospace applications, SAW models have been developed. This paper reports on the comparison of three methods of modeling SAWs. The three models are the Impulse Response Method (a first order model), and two second order matrix methods; the conventional matrix approach, and a modified matrix approach that is extended to include internal finger reflections. The second order models are based upon matrices that were originally developed for analyzing microwave circuits using transmission line theory. Results from the models are presented with measured data from devices. Keywords: Surface Acoustic Wave, SAW, transmission line models, Impulse Response Method.
Transmission Model of Hepatitis B Virus with the Migration Effect
Directory of Open Access Journals (Sweden)
Muhammad Altaf Khan
2013-01-01
Full Text Available Hepatitis B is a globally infectious disease. Mathematical modeling of HBV transmission is an interesting research area. In this paper, we present characteristics of HBV virus transmission in the form of a mathematical model. We analyzed the effect of immigrants in the model to study the effect of immigrants for the host population. We added the following flow parameters: “the transmission between migrated and exposed class” and “the transmission between migrated and acute class.” With these new features, we obtained a compartment model of six differential equations. First, we find the basic threshold quantity Ro and then find the local asymptotic stability of disease-free equilibrium and endemic equilibrium. Furthermore, we find the global stability of the disease-free and endemic equilibria. Previous similar publications have not added the kind of information about the numerical results of the model. In our case, from numerical simulation, a detailed discussion of the parameters and their numerical results is presented. We claim that with these assumptions and by adding the migrated class, the model informs policy for governments, to be aware of the immigrants and subject them to tests about the disease status. Immigrants for short visits and students should be subjected to tests to reduce the number of immigrants with disease.
Study on Tower Models for EHV Transmission Line
Directory of Open Access Journals (Sweden)
Xu Bao-Qing
2016-01-01
Full Text Available Lightning outage accident is one of the main factors that threat seriously the safe and reliable operation of power system. So it is very important to establish reasonable transmission tower model and evaluate the impulse response characteristic of lightning wave traveling on the transmission tower properly for determining reliable lightning protection performance. With the help of Electromagnetic Transient Program (EMTP, six 500kV tower models are built. Aiming at one line to one transformer operating mode of 500kV substation, the intruding wave overvoltage under different tower models is calculated. The effect of tower model on intruding overvoltage has been studied. The results show that different tower models can result in great differences to the calculation results. Hence, reasonable selection of the tower model in the calculation of back- strike intruding wave is very important.
Shi, Wenxiong; Huang, Xianfu; Liu, Zhanwei
2014-05-05
Quantitatively measuring a dynamic liquid surface often presents a challenge due to high transparency, fluidity and specular reflection. Here, a novel Transmission-Lattice based Geometric Phase Analysis (TLGPA) method is introduced. In this method, a special lattice is placed underneath a liquid to be tested and, when viewed from above, the phase of the transmission-lattice image is modulated by the deformation of the liquid surface. Combining this with multi-directional Newton iteration algorithms, the dynamic deformation field of the liquid surface can be calculated from the phase variation of a series of transmission-lattice images captured at different moments. The developed method has the advantage of strong self-adaption ability to initial lattice rotational errors and this is discussed in detail. Dynamic 3D ripples formation and propagation was investigated and the results obtained demonstrated the feasibility of the method.
Hybrid dynamics for currency modeling
Theodosopoulos, Ted; Trifunovic, Alex
2006-01-01
We present a simple hybrid dynamical model as a tool to investigate behavioral strategies based on trend following. The multiplicative symbolic dynamics are generated using a lognormal diffusion model for the at-the-money implied volatility term structure. Thus, are model exploits information from derivative markets to obtain qualititative properties of the return distribution for the underlier. We apply our model to the JPY-USD exchange rate and the corresponding 1mo., 3mo., 6mo. and 1yr. im...
HIV Transmission Dynamics Among Foreign-Born Persons in the United States.
Valverde, Eduardo E; Oster, Alexandra M; Xu, Songli; Wertheim, Joel O; Hernandez, Angela L
2017-12-15
In the United States (US), foreign-born persons are disproportionately affected by HIV and differ epidemiologically from US-born persons with diagnosed HIV infection. Understanding HIV transmission dynamics among foreign-born persons is important to guide HIV prevention efforts for these populations. We conducted molecular transmission network analysis to describe HIV transmission dynamics among foreign-born persons with diagnosed HIV. Using HIV-1 polymerase nucleotide sequences reported to the US National HIV Surveillance System for persons with diagnosed HIV infection during 2001-2013, we constructed a genetic distance-based transmission network using HIV-TRACE and examined the birth region of potential transmission partners in this network. Of 77,686 people, 12,064 (16%) were foreign born. Overall, 28% of foreign-born persons linked to at least one other person in the transmission network. Of potential transmission partners, 62% were born in the United States, 31% were born in the same region as the foreign-born person, and 7% were born in another region of the world. Most transmission partners of male foreign-born persons (63%) were born in the United States, whereas most transmission partners of female foreign-borns (57%) were born in their same world region. These finding suggests that a majority of HIV infections among foreign-born persons in our network occurred after immigrating to the United States. Efforts to prevent HIV infection among foreign-born persons in the United States should include information of the transmission networks in which these individuals acquire or transmit HIV to develop more targeted HIV prevention interventions.
Some Advances in the Circuit Modeling of Extraordinary Optical Transmission
Directory of Open Access Journals (Sweden)
F. Medina
2009-06-01
Full Text Available The phenomenon of extraordinary optical transmission (EOT through electrically small holes perforated on opaque metal screens has been a hot topic in the optics community for more than one decade. This experimentally observed frequency-selective enhanced transmission of electromagnetic power through holes, for which classical Bethe's theory predicts very poor transmission, later attracted the attention of engineers working on microwave engineering or applied electromagnetics. Extraordinary transmission was ﬁrst linked to the plasma-like behavior of metals at optical frequencies. However, the primary role played by the periodicity of the distribution of holes was soon made evident, in such a way that extraordinary transmission was disconnected from the particular behavior of metals at optical frequencies. Indeed, the same phenomenon has been observed in the microwave and millimeter wave regime, for instance. Nowadays, the most commonly accepted theory explains EOT in terms of the interaction of the impinging plane wave with the surface plasmon-polariton-Bloch waves (SPP-Bloch supported by the periodically perforated plate. The authors of this paper have recently proposed an alternative model whose details will be brieﬂy summarized here. A parametric study of the predictions of the model and some new potential extensions will be reported to provide additional insight.
Kwok, Kin On; Read, Jonathan M; Tang, Arthur; Chen, Hong; Riley, Steven; Kam, Kai Man
2018-04-18
Non-hospital residential facilities are important reservoirs for MRSA transmission. However, conclusions and public health implications drawn from the many mathematical models depicting nosocomial MRSA transmission may not be applicable to these settings. Therefore, we reviewed the MRSA transmission dynamics studies in defined non-hospital residential facilities to: (1) provide an overview of basic epidemiology which has been addressed; (2) identify future research direction; and (3) improve future model implementation. A review was conducted by searching related keywords in PUBMED without time restriction as well as internet searches via Google search engine. We included only articles describing the epidemiological transmission pathways of MRSA/community-associated MRSA within and between defined non-hospital residential settings. Among the 10 included articles, nursing homes (NHs) and correctional facilities (CFs) were two settings considered most frequently. Importation of colonized residents was a plausible reason for MRSA outbreaks in NHs, where MRSA was endemic without strict infection control interventions. The importance of NHs over hospitals in increasing nosocomial MRSA prevalence was highlighted. Suggested interventions in NHs included: appropriate staffing level, screening and decolonizing, and hand hygiene. On the other hand, the small population amongst inmates in CFs has no effect on MRSA community transmission. Included models ranged from system-level compartmental models to agent-based models. There was no consensus over the course of disease progression in these models, which were mainly featured with NH residents /CF inmates/ hospital patients as transmission pathways. Some parameters used by these models were outdated or unfit. Importance of NHs has been highlighted from these current studies addressing scattered aspects of MRSA epidemiology. However, the wide variety of non-hospital residential settings suggest that more work is needed before
Telomere dynamics and homeostasis in a transmissible cancer.
Ujvari, Beata; Pearse, Anne-Maree; Taylor, Robyn; Pyecroft, Stephen; Flanagan, Cassandra; Gombert, Sara; Papenfuss, Anthony T; Madsen, Thomas; Belov, Katherine
2012-01-01
Devil Facial Tumour Disease (DFTD) is a unique clonal cancer that threatens the world's largest carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii) with extinction. This transmissible cancer is passed between individual devils by cell implantation during social interactions. The tumour arose in a Schwann cell of a single devil over 15 years ago and since then has expanded clonally, without showing signs of replicative senescence; in stark contrast to a somatic cell that displays a finite capacity for replication, known as the "Hayflick limit". In the present study we investigate the role of telomere length, measured as Telomere Copy Number (TCN), and telomerase and shelterin gene expression, as well as telomerase activity in maintaining hyperproliferation of Devil Facial Tumour (DFT) cells. Our results show that DFT cells have short telomeres. DFTD TCN does not differ between geographic regions or between strains. However, TCN has increased over time. Unlimited cell proliferation is likely to have been achieved through the observed up-regulation of the catalytic subunit of telomerase (TERT) and concomitant activation of telomerase. Up-regulation of the central component of shelterin, the TRF1-intercating nuclear factor 2 (TINF2) provides DFT a mechanism for telomere length homeostasis. The higher expression of both TERT and TINF2 may also protect DFT cells from genomic instability and enhance tumour proliferation. DFT cells appear to monitor and regulate the length of individual telomeres: i.e. shorter telomeres are elongated by up-regulation of telomerase-related genes; longer telomeres are protected from further elongation by members of the shelterin complex, which may explain the lack of spatial and strain variation in DFT telomere copy number. The observed longitudinal increase in gene expression in DFT tissue samples and telomerase activity in DFT cell lines might indicate a selection for more stable tumours with higher proliferative potential.
Telomere dynamics and homeostasis in a transmissible cancer.
Directory of Open Access Journals (Sweden)
Beata Ujvari
Full Text Available Devil Facial Tumour Disease (DFTD is a unique clonal cancer that threatens the world's largest carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii with extinction. This transmissible cancer is passed between individual devils by cell implantation during social interactions. The tumour arose in a Schwann cell of a single devil over 15 years ago and since then has expanded clonally, without showing signs of replicative senescence; in stark contrast to a somatic cell that displays a finite capacity for replication, known as the "Hayflick limit".In the present study we investigate the role of telomere length, measured as Telomere Copy Number (TCN, and telomerase and shelterin gene expression, as well as telomerase activity in maintaining hyperproliferation of Devil Facial Tumour (DFT cells. Our results show that DFT cells have short telomeres. DFTD TCN does not differ between geographic regions or between strains. However, TCN has increased over time. Unlimited cell proliferation is likely to have been achieved through the observed up-regulation of the catalytic subunit of telomerase (TERT and concomitant activation of telomerase. Up-regulation of the central component of shelterin, the TRF1-intercating nuclear factor 2 (TINF2 provides DFT a mechanism for telomere length homeostasis. The higher expression of both TERT and TINF2 may also protect DFT cells from genomic instability and enhance tumour proliferation.DFT cells appear to monitor and regulate the length of individual telomeres: i.e. shorter telomeres are elongated by up-regulation of telomerase-related genes; longer telomeres are protected from further elongation by members of the shelterin complex, which may explain the lack of spatial and strain variation in DFT telomere copy number. The observed longitudinal increase in gene expression in DFT tissue samples and telomerase activity in DFT cell lines might indicate a selection for more stable tumours with higher proliferative
Directory of Open Access Journals (Sweden)
Xinwei Wang
2017-01-01
Full Text Available Topology detection for output-coupling weighted complex dynamical networks with two types of time delays is investigated in this paper. Different from existing literatures, coupling delay and transmission delay are simultaneously taken into account in the output-coupling network. Based on the idea of the state observer, we build the drive-response system and apply LaSalle’s invariance principle to the error dynamical system of the drive-response system. Several convergent criteria are deduced in the form of algebraic inequalities. Some numerical simulations for the complex dynamical network, with node dynamics being chaotic, are given to verify the effectiveness of the proposed scheme.
The fusion rate in the transmission resonance model
International Nuclear Information System (INIS)
Jaendel, M.
1992-01-01
Resonant transmission of deuterons through a chain of target deuterons in a metal matrix has been suggested as an explanation for the cold fusion phenomena. In this paper the fusion rate in such transmission resonance models is estimated, and the basic physical constraints are discussed. The dominating contribution to the fusion yield is found to come from metastable states. The fusion rate is well described by the Wentzel-Kramer-Brillouin approximation and appears to be much too small to explain the experimental anomalies
Computer Modelling of Dynamic Processes
Directory of Open Access Journals (Sweden)
B. Rybakin
2000-10-01
Full Text Available Results of numerical modeling of dynamic problems are summed in the article up. These problems are characteristic for various areas of human activity, in particular for problem solving in ecology. The following problems are considered in the present work: computer modeling of dynamic effects on elastic-plastic bodies, calculation and determination of performances of gas streams in gas cleaning equipment, modeling of biogas formation processes.
International Nuclear Information System (INIS)
Antonini, C; Persico, G; Rowe, A L
2008-01-01
Among the measurement and control systems of gas turbine engines, a recent new issue is the possibility of performing unsteady pressure measurements to detect flow anomalies in an engine or to evaluate loads on aerodynamic surfaces. A possible answer to this demand could be extending the use of well known and widely used transmission line systems, which have been applied so far to steady monitoring, to unsteady measurements thanks to proper dynamic modeling and compensation. Despite the huge number of models existing in the literature, a novel method has been developed, which is at the same time easy-to-handle, flexible and capable of reproducing the actual physics of the problem. Furthermore, the new model is able to deal with arbitrary complex networks of lines and cavities, and thus its applicability is not limited to series-connected systems. The main objectives of this paper are to show the derivation of the model, its validation against experimental tests and example of its applicability
The evolution of wealth transmission in human populations: a stochastic model
International Nuclear Information System (INIS)
Augustins, G; Etienne, L; Ferrer, R; Godelle, B; Rousset, F; Ferdy, J-B; Pitard, E
2014-01-01
Reproductive success and survival are influenced by wealth in human populations. Wealth is transmitted to offsprings and strategies of transmission vary over time and among populations, the main variation being how equally wealth is transmitted to children. Here we propose a model where we simulate both the dynamics of wealth in a population and the evolution of a trait that determines how wealth is transmitted from parents to offspring, in a darwinian context
Analytical Model for High Impedance Fault Analysis in Transmission Lines
Directory of Open Access Journals (Sweden)
S. Maximov
2014-01-01
Full Text Available A high impedance fault (HIF normally occurs when an overhead power line physically breaks and falls to the ground. Such faults are difficult to detect because they often draw small currents which cannot be detected by conventional overcurrent protection. Furthermore, an electric arc accompanies HIFs, resulting in fire hazard, damage to electrical devices, and risk with human life. This paper presents an analytical model to analyze the interaction between the electric arc associated to HIFs and a transmission line. A joint analytical solution to the wave equation for a transmission line and a nonlinear equation for the arc model is presented. The analytical model is validated by means of comparisons between measured and calculated results. Several cases of study are presented which support the foundation and accuracy of the proposed model.
Spatial modelling and ecology of Echinococcus multilocularis transmission in China.
Danson, F Mark; Giraudoux, Patrick; Craig, Philip S
2006-01-01
Recent research in central China has suggested that the most likely transmission mechanism for Echinococcus multilocularis to humans is via domestic dogs which are allowed to roam freely and hunt (infected) small mammals within areas close to villages or in areas of tented pasture. This assertion has led to the hypothesis that there is a landscape control on transmission risk since the proximity of suitable habitat for susceptible small mammals appears to be the key. We have tested this hypothesis in a number of endemic areas in China, notably south Gansu Province and the Tibetan region of western Sichuan Province. The fundamental landscape control is its effect at a regional scale on small mammal species assemblages (susceptible species are not ubiquitous) and, at a local scale, the spatial distributions of small mammal populations. To date the research has examined relationships between landscape composition and patterns of human infection, landscape and small mammal distributions and recently the relationships between landscape and dog infection rates. The key tool to characterize landscape is satellite remote sensing and these data are used as inputs to drive spatial models of transmission risk. This paper reviews the progress that has been made so far in spatial modeling of the ecology of E. multilocularis with particular reference to China, outlines current research issues, and describes a framework for building a spatial-temporal model of transmission ecology.
Hone, J; Pech, R; Yip, P
1992-04-01
Infectious diseases establish in a population of wildlife hosts when the number of secondary infections is greater than or equal to one. To estimate whether establishment will occur requires extensive experience or a mathematical model of disease dynamics and estimates of the parameters of the disease model. The latter approach is explored here. Methods for estimating key model parameters, the transmission coefficient (beta) and the basic reproductive rate (RDRS), are described using classical swine fever (hog cholera) in wild pigs as an example. The tentative results indicate that an acute infection of classical swine fever will establish in a small population of wild pigs. Data required for estimation of disease transmission rates are reviewed and sources of bias and alternative methods discussed. A comprehensive evaluation of the biases and efficiencies of the methods is needed.
High-speed nanoscale characterization of dewetting via dynamic transmission electron microscopy
International Nuclear Information System (INIS)
Hihath, Sahar; Santala, Melissa K.; Campbell, Geoffrey; Benthem, Klaus van
2016-01-01
The dewetting of thin films can occur in either the solid or the liquid state for which different mass transport mechanisms are expected to control morphological changes. Traditionally, dewetting dynamics have been examined on time scales between several seconds to hours, and length scales ranging between nanometers and millimeters. The determination of mass transport mechanisms on the nanoscale, however, requires nanoscale spatial resolution and much shorter time scales. This study reports the high-speed observation of dewetting phenomena for kinetically constrained Ni thin films on crystalline SrTiO_3 substrates. Movie-mode Dynamic Transmission Electron Microscopy (DTEM) was used for high-speed image acquisition during thin film dewetting at different temperatures. DTEM imaging confirmed that the initial stages of film agglomeration include edge retraction, hole formation, and growth. Finite element modeling was used to simulate temperature distributions within the DTEM samples after laser irradiation with different energies. For pulsed laser irradiation at 18 μJ, experimentally observed hole growth suggests that Marangoni flow dominates hole formation in the liquid nickel film. After irradiation with 13.8 μJ, however, the observations suggest that dewetting was initiated by nucleation of voids followed by hole growth through solid-state surface diffusion.
High-speed nanoscale characterization of dewetting via dynamic transmission electron microscopy
Energy Technology Data Exchange (ETDEWEB)
Hihath, Sahar [Department of Materials Science and Engineering, University of California, Davis, 1 Shields Ave., Davis, California 95616 (United States); Department of Physics, University of California, Davis, 1 Shields Ave., Davis, California 95616 (United States); Santala, Melissa K.; Campbell, Geoffrey [Materials Science Division, Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); Benthem, Klaus van, E-mail: benthem@ucdavis.edu [Department of Materials Science and Engineering, University of California, Davis, 1 Shields Ave., Davis, California 95616 (United States)
2016-08-28
The dewetting of thin films can occur in either the solid or the liquid state for which different mass transport mechanisms are expected to control morphological changes. Traditionally, dewetting dynamics have been examined on time scales between several seconds to hours, and length scales ranging between nanometers and millimeters. The determination of mass transport mechanisms on the nanoscale, however, requires nanoscale spatial resolution and much shorter time scales. This study reports the high-speed observation of dewetting phenomena for kinetically constrained Ni thin films on crystalline SrTiO{sub 3} substrates. Movie-mode Dynamic Transmission Electron Microscopy (DTEM) was used for high-speed image acquisition during thin film dewetting at different temperatures. DTEM imaging confirmed that the initial stages of film agglomeration include edge retraction, hole formation, and growth. Finite element modeling was used to simulate temperature distributions within the DTEM samples after laser irradiation with different energies. For pulsed laser irradiation at 18 μJ, experimentally observed hole growth suggests that Marangoni flow dominates hole formation in the liquid nickel film. After irradiation with 13.8 μJ, however, the observations suggest that dewetting was initiated by nucleation of voids followed by hole growth through solid-state surface diffusion.
Predictive modeling of mosquito abundance and dengue transmission in Kenya
Caldwell, J.; Krystosik, A.; Mutuku, F.; Ndenga, B.; LaBeaud, D.; Mordecai, E.
2017-12-01
Approximately 390 million people are exposed to dengue virus every year, and with no widely available treatments or vaccines, predictive models of disease risk are valuable tools for vector control and disease prevention. The aim of this study was to modify and improve climate-driven predictive models of dengue vector abundance (Aedes spp. mosquitoes) and viral transmission to people in Kenya. We simulated disease transmission using a temperature-driven mechanistic model and compared model predictions with vector trap data for larvae, pupae, and adult mosquitoes collected between 2014 and 2017 at four sites across urban and rural villages in Kenya. We tested predictive capacity of our models using four temperature measurements (minimum, maximum, range, and anomalies) across daily, weekly, and monthly time scales. Our results indicate seasonal temperature variation is a key driving factor of Aedes mosquito abundance and disease transmission. These models can help vector control programs target specific locations and times when vectors are likely to be present, and can be modified for other Aedes-transmitted diseases and arboviral endemic regions around the world.
Broens, E.M.
2011-01-01
In 2004, an association between human carriage of methicillin resistant Staphylococcus aureus (MRSA) and contact with pigs was found. To assess the implications of this finding for veterinary and public health more insight into the prevalence, risk factors and transmission dynamics of
Light aircraft sound transmission studies - Noise reduction model
Atwal, Mahabir S.; Heitman, Karen E.; Crocker, Malcolm J.
1987-01-01
Experimental tests conducted on the fuselage of a single-engine Piper Cherokee light aircraft suggest that the cabin interior noise can be reduced by increasing the transmission loss of the dominant sound transmission paths and/or by increasing the cabin interior sound absorption. The validity of using a simple room equation model to predict the cabin interior sound-pressure level for different fuselage and exterior sound field conditions is also presented. The room equation model is based on the sound power flow balance for the cabin space and utilizes the measured transmitted sound intensity data. The room equation model predictions were considered good enough to be used for preliminary acoustical design studies.
Leaf transmission reduction using moving jaws for dynamic MLC IMRT
International Nuclear Information System (INIS)
Schmidhalter, D.; Fix, M. K.; Niederer, P.; Mini, R.; Manser, P.
2007-01-01
The aim of this work is to investigate to what extent it is possible to use the secondary collimator jaws to reduce the transmitted radiation through the multileaf collimator (MLC) during an intensity modulated radiation therapy (IMRT). A method is developed and introduced where the jaws follow the open window of the MLC dynamically (dJAW method). With the aid of three academic cases (Closed MLC, Sliding-gap, and Chair) and two clinical cases (prostate and head and neck) the feasibility of the dJAW method and the influence of this method on the applied dose distributions are investigated. For this purpose the treatment planning system Eclipse and the Research-Toolbox were used as well as measurements within a solid water phantom were performed. The transmitted radiation through the closed MLC leads to an inhomogeneous dose distribution. In this case, the measured dose within a plane perpendicular to the central axis differs up to 40% (referring to the maximum dose within this plane) for 6 and 15 MV. The calculated dose with Eclipse is clearly more homogeneous. For the Sliding-gap case this difference is still up to 9%. Among other things, these differences depend on the depth of the measurement within the solid water phantom and on the application method. In the Chair case, the dose in regions where no dose is desired is locally reduced by up to 50% using the dJAW method instead of the conventional method. The dose inside the chair-shaped region decreased up to 4% if the same number of monitor units (MU) as for the conventional method was applied. The undesired dose in the volume body minus the planning target volume in the clinical cases prostate and head and neck decreased up to 1.8% and 1.5%, while the number of the applied MU increased up to 3.1% and 2.8%, respectively. The new dJAW method has the potential to enhance the optimization of the conventional IMRT to a further step
Electricity market equilibrium model with resource constraint and transmission congestion
Energy Technology Data Exchange (ETDEWEB)
Gao, F. [ABB, Inc., Santa Clara, CA 95050 (United States); Sheble, G.B. [Portland State University, Portland, OR 97207 (United States)
2010-01-15
Electricity market equilibrium model not only helps Independent System Operator/Regulator analyze market performance and market power, but also provides Market Participants the ability to build optimal bidding strategies based on Microeconomics analysis. Supply Function Equilibrium (SFE) is attractive compared to traditional models and many efforts have been made on it before. However, most past research focused on a single-period, single-market model and did not address the fact that GENCOs hold a portfolio of assets in both electricity and fuel markets. This paper first identifies a proper SFE model, which can be applied to a multiple-period situation. Then the paper develops the equilibrium condition using discrete time optimal control considering fuel resource constraints. Finally, the paper discusses the issues of multiple equilibria caused by transmission network and shows that a transmission constrained equilibrium may exist, however the shadow price may not be zero. Additionally, an advantage from the proposed model for merchant transmission planning is discussed. (author)
Electricity market equilibrium model with resource constraint and transmission congestion
International Nuclear Information System (INIS)
Gao, F.; Sheble, G.B.
2010-01-01
Electricity market equilibrium model not only helps Independent System Operator/Regulator analyze market performance and market power, but also provides Market Participants the ability to build optimal bidding strategies based on Microeconomics analysis. Supply Function Equilibrium (SFE) is attractive compared to traditional models and many efforts have been made on it before. However, most past research focused on a single-period, single-market model and did not address the fact that GENCOs hold a portfolio of assets in both electricity and fuel markets. This paper first identifies a proper SFE model, which can be applied to a multiple-period situation. Then the paper develops the equilibrium condition using discrete time optimal control considering fuel resource constraints. Finally, the paper discusses the issues of multiple equilibria caused by transmission network and shows that a transmission constrained equilibrium may exist, however the shadow price may not be zero. Additionally, an advantage from the proposed model for merchant transmission planning is discussed. (author)
Structural dynamic modifications via models
Indian Academy of Sciences (India)
The study shows that as many as half of the matrix ... the dynamicist's analytical modelling skill which would appear both in the numerator as. Figure 2. ..... Brandon J A 1990 Strategies for structural dynamic modification (New York: John Wiley).
Dynamic programming models and applications
Denardo, Eric V
2003-01-01
Introduction to sequential decision processes covers use of dynamic programming in studying models of resource allocation, methods for approximating solutions of control problems in continuous time, production control, more. 1982 edition.
Efficient simulation of the spatial transmission dynamics of influenza.
Directory of Open Access Journals (Sweden)
Meng-Tsung Tsai
2010-11-01
Full Text Available Early data from the 2009 H1N1 pandemic (H1N1pdm suggest that previous studies over-estimated the within-country rate of spatial spread of pandemic influenza. As large spatially resolved data sets are constructed, the need for efficient simulation code with which to investigate the spatial patterns of the pandemic becomes clear. Here, we present a significant improvement to the efficiency of an individual-based stochastic disease simulation framework commonly used in multiple previous studies. We quantify the efficiency of the revised algorithm and present an alternative parameterization of the model in terms of the basic reproductive number. We apply the model to the population of Taiwan and demonstrate how the location of the initial seed can influence spatial incidence profiles and the overall spread of the epidemic. Differences in incidence are driven by the relative connectivity of alternate seed locations. The ability to perform efficient simulation allows us to run a batch of simulations and take account of their average in real time. The averaged data are stable and can be used to differentiate spreading patterns that are not readily seen by only conducting a few runs.
Assessing the impact of homelessness on HIV/AIDS transmission dynamics
Directory of Open Access Journals (Sweden)
C.P. Bhunu
2015-12-01
Full Text Available Care for the people living with HIV/AIDS is more than the provision of antiretroviral therapy. The effects of homelessness on HIV/AIDS transmission are captured through a mathematical model. The mathematical model is rigorously analyzed. The disease-free equilibrium is globally asymptotically stable when the reproduction number is less than unity. Results from the analysis of the reproduction number suggests that homelessness enhances both HIV transmission and progression to the AIDS stage. This is further supported by numerical simulations which show that some elements of homelessness (lack of entertainment enhances HIV/AIDS transmission.
Dynamical models of the Galaxy
Directory of Open Access Journals (Sweden)
McMillan P.J.
2012-02-01
Full Text Available I discuss the importance of dynamical models for exploiting survey data, focusing on the advantages of “torus” models. I summarize a number of applications of these models to the study of the Milky Way, including the determination of the peculiar Solar velocity and investigation of the Hyades moving group.
Assessing the impact of homelessness on HIV/AIDS transmission dynamics
C.P. Bhunu
2015-01-01
Care for the people living with HIV/AIDS is more than the provision of antiretroviral therapy. The effects of homelessness on HIV/AIDS transmission are captured through a mathematical model. The mathematical model is rigorously analyzed. The disease-free equilibrium is globally asymptotically stable when the reproduction number is less than unity. Results from the analysis of the reproduction number suggests that homelessness enhances both HIV transmission and progression to the AIDS stage. T...
Rúa-Uribe, Guillermo L; Suárez-Acosta, Carolina; Chauca, José; Ventosilla, Palmira; Almanza, Rita
2013-09-01
Dengue fever is a major impact on public health vector-borne disease, and its transmission is influenced by entomological, sociocultural and economic factors. Additionally, climate variability plays an important role in the transmission dynamics. A large scientific consensus has indicated that the strong association between climatic variables and disease could be used to develop models to explain the incidence of the disease. To develop a model that provides a better understanding of dengue transmission dynamics in Medellin and predicts increases in the incidence of the disease. The incidence of dengue fever was used as dependent variable, and weekly climatic factors (maximum, mean and minimum temperature, relative humidity and precipitation) as independent variables. Expert Modeler was used to develop a model to better explain the behavior of the disease. Climatic variables with significant association to the dependent variable were selected through ARIMA models. The model explains 34% of observed variability. Precipitation was the climatic variable showing statistically significant association with the incidence of dengue fever, but with a 20 weeks delay. In Medellin, the transmission of dengue fever was influenced by climate variability, especially precipitation. The strong association dengue fever/precipitation allowed the construction of a model to help understand dengue transmission dynamics. This information will be useful to develop appropriate and timely strategies for dengue control.
Sound transmission through lightweight double-leaf partitions: theoretical modelling
Wang, J.; Lu, T. J.; Woodhouse, J.; Langley, R. S.; Evans, J.
2005-09-01
This paper presents theoretical modelling of the sound transmission loss through double-leaf lightweight partitions stiffened with periodically placed studs. First, by assuming that the effect of the studs can be replaced with elastic springs uniformly distributed between the sheathing panels, a simple smeared model is established. Second, periodic structure theory is used to develop a more accurate model taking account of the discrete placing of the studs. Both models treat incident sound waves in the horizontal plane only, for simplicity. The predictions of the two models are compared, to reveal the physical mechanisms determining sound transmission. The smeared model predicts relatively simple behaviour, in which the only conspicuous features are associated with coincidence effects with the two types of structural wave allowed by the partition model, and internal resonances of the air between the panels. In the periodic model, many more features are evident, associated with the structure of pass- and stop-bands for structural waves in the partition. The models are used to explain the effects of incidence angle and of the various system parameters. The predictions are compared with existing test data for steel plates with wooden stiffeners, and good agreement is obtained.
Mathematical models for lymphatic filariasis transmission and control: Challenges and prospects
Directory of Open Access Journals (Sweden)
Kaliannagounder Krishnamoorthy
2008-02-01
Full Text Available Abstract Background Mathematical models developed for describing the dynamics of transmission, infection, disease and control of lymphatic filariasis (LF gained momentum following the 1997 World Health Assembly resolution and the launching of the Global Programme to Eliminate Lymphatic Filariasis (GPELF in 2000. Model applications could provide valuable inputs for making decisions while implementing large scale programmes. However these models need to be evaluated at different epidemiological settings for optimization and fine-tuning with new knowledge and understanding on infection/disease dynamics. Discussion EPIFIL and LYMFASIM are the two mathematical simulation models currently available for lymphatic filariasis transmission and control. Both models have been used for prediction and evaluation of control programmes under research settings. Their widespread application in evaluating large-scale elimination programmes warrants validation of assumptions governing the dynamics of infection and disease in different epidemiological settings. Furthermore, the predictive power of the models for decision support can be enhanced by generating knowledge on some important issues that pose challenges and incorporating such knowledge into the models. We highlight factors related to the efficacy of the drugs of choice, their mode of action, and the possibility that drug resistance may develop; the role of vector-parasite combinations; the magnitude of transmission thresholds; host-parasite interactions and their effects on the dynamics of infection and immunity; parasite biology, and progression to LF-associated disease. Summary The two mathematical models developed offer potential decision making tools for transmission and control of LF. In view of the goals of the GPELF, the predictive power of these models needs to be enhanced for their wide-spread application in large scale programmes. Assimilation and translation of new information into the models is
Correction for dynamic bias error in transmission measurements of void fraction
International Nuclear Information System (INIS)
Andersson, P.; Sundén, E. Andersson; Svärd, S. Jacobsson; Sjöstrand, H.
2012-01-01
Dynamic bias errors occur in transmission measurements, such as X-ray, gamma, or neutron radiography or tomography. This is observed when the properties of the object are not stationary in time and its average properties are assessed. The nonlinear measurement response to changes in transmission within the time scale of the measurement implies a bias, which can be difficult to correct for. A typical example is the tomographic or radiographic mapping of void content in dynamic two-phase flow systems. In this work, the dynamic bias error is described and a method to make a first-order correction is derived. A prerequisite for this method is variance estimates of the system dynamics, which can be obtained using high-speed, time-resolved data acquisition. However, in the absence of such acquisition, a priori knowledge might be used to substitute the time resolved data. Using synthetic data, a void fraction measurement case study has been simulated to demonstrate the performance of the suggested method. The transmission length of the radiation in the object under study and the type of fluctuation of the void fraction have been varied. Significant decreases in the dynamic bias error were achieved to the expense of marginal decreases in precision.
Dynamics of host-reservoir transmission of Ebola with spillover potential to humans
Directory of Open Access Journals (Sweden)
Berge Tsanou
2018-04-01
Full Text Available Ebola virus disease (EVD is a zoonotic borne disease (i.e. disease that is spread from animals to people. Therefore human beings can be infected through direct contact with an infected animal (fruit-eating bat or great ape. It has been demonstrated that fruit-eating bats of pteropodidae family are potential reservoir of EVD. Moreover, it has been biologically shown that fruit-eating bats do not die due to EVD and bear the Ebola viruses lifelong. We develop in this paper, a mathematical model to assess the impact of the reservoir on the dynamics of EVD. Our model couples a bat-to-bat model with a human-to-human model and the indirect environmental contamination through a spillover process (i.e. process by which a zoonotic pathogen moves (regardless of transmission mode from an animal host (or environmental reservoir to a human host from bats to humans. The sub-models and the coupled models exhibit each a threshold behavior with the corresponding basic reproduction numbers being the bifurcation parameters. Existence of equilibria, their global stability are established by combining monotone operator theory, Lyapunov-LaSalle techniques and graph theory. Control strategies are assessed by using the target reproduction numbers. The efforts required to control EVD are assessed as well through S-control. The spillover event is shown to be highly detrimental to EVD by allowing the disease to switch from bats to humans even though the disease was not initially endemic in the human population. Precisely, we show that the spillover phenomenon contributes to speed up the disease outbreak. This suggests that the manipulation and consumption of fruit-bats play an important role in sustaining EVD in a given environment.
Animal models for oral transmission of Listeria monocytogenes
Directory of Open Access Journals (Sweden)
Sarah E F D'Orazio
2014-02-01
Full Text Available Listeria monocytogenes has been recognized as a food borne pathogen in humans since the 1980s, but we still understand very little about oral transmission of L. monocytogenes or the host factors that determine susceptibility to gastrointestinal infection, due to the lack of an appropriate small animal model of oral listeriosis. Early feeding trials suggested that many animals were highly resistant to oral infection, and the more reproducible intravenous or intraperitoneal routes of inoculation soon came to be favored. There are a fair number of previously published studies using an oral infection route, but the work varies widely in terms of bacterial strain choice, the methods used for oral transmission, and various manipulations used to enhance infectivity. This mini review will summarize the published literature using oral routes of L. monocytogenes infection and will highlight recent technological advances that have made oral infection a more attractive model system.
A rumor transmission model with incubation in social networks
Jia, Jianwen; Wu, Wenjiang
2018-02-01
In this paper, we propose a rumor transmission model with incubation period and constant recruitment in social networks. By carrying out an analysis of the model, we study the stability of rumor-free equilibrium and come to the local stable condition of the rumor equilibrium. We use the geometric approach for ordinary differential equations for showing the global stability of the rumor equilibrium. And when ℜ0 = 1, the new model occurs a transcritical bifurcation. Furthermore, numerical simulations are used to support the analysis. At last, some conclusions are presented.
Method of modeling transmissions for real-time simulation
Hebbale, Kumaraswamy V.
2012-09-25
A transmission modeling system includes an in-gear module that determines an in-gear acceleration when a vehicle is in gear. A shift module determines a shift acceleration based on a clutch torque when the vehicle is shifting between gears. A shaft acceleration determination module determines a shaft acceleration based on at least one of the in-gear acceleration and the shift acceleration.
Transmission of severe acute respiratory syndrome in dynamical small-world networks
Masuda, Naoki; Konno, Norio; Aihara, Kazuyuki
2004-03-01
The outbreak of severe acute respiratory syndrome (SARS) is still threatening the world because of a possible resurgence. In the current situation that effective medical treatments such as antiviral drugs are not discovered yet, dynamical features of the epidemics should be clarified for establishing strategies for tracing, quarantine, isolation, and regulating social behavior of the public at appropriate costs. Here we propose a network model for SARS epidemics and discuss why superspreaders emerged and why SARS spread especially in hospitals, which were key factors of the recent outbreak. We suggest that superspreaders are biologically contagious patients, and they may amplify the spreads by going to potentially contagious places such as hospitals. To avoid mass transmission in hospitals, it may be a good measure to treat suspected cases without hospitalizing them. Finally, we indicate that SARS probably propagates in small-world networks associated with human contacts and that the biological nature of individuals and social group properties are factors more important than the heterogeneous rates of social contacts among individuals. This is in marked contrast with epidemics of sexually transmitted diseases or computer viruses to which scale-free network models often apply.
Dynamics of a split torque helicopter transmission. M.S. Thesis - Cleveland State Univ.
Krantz, Timothy L.
1994-01-01
Split torque designs, proposed as alternatives to traditional planetary designs for helicopter main rotor transmissions, can save weight and be more reliable than traditional designs. This report presents the results of an analytical study of the system dynamics and performance of a split torque gearbox that uses a balance beam mechanism for load sharing. The Lagrange method was applied to develop a system of equations of motion. The mathematical model includes time-varying gear mesh stiffness, friction, and manufacturing errors. Cornell's method for calculating the stiffness of spur gear teeth was extended and applied to helical gears. The phenomenon of sidebands spaced at shaft frequencies about gear mesh fundamental frequencies was simulated by modeling total composite gear errors as sinusoid functions. Although the gearbox has symmetric geometry, the loads and motions of the two power paths differ. Friction must be considered to properly evaluate the balance beam mechanism. For the design studied, the balance beam is not an effective device for load sharing unless the coefficient of friction is less than 0.003. The complete system stiffness as represented by the stiffness matrix used in this analysis must be considered to precisely determine the optimal tooth indexing position.
Mathematical models for therapeutic approaches to control HIV disease transmission
Roy, Priti Kumar
2015-01-01
The book discusses different therapeutic approaches based on different mathematical models to control the HIV/AIDS disease transmission. It uses clinical data, collected from different cited sources, to formulate the deterministic as well as stochastic mathematical models of HIV/AIDS. It provides complementary approaches, from deterministic and stochastic points of view, to optimal control strategy with perfect drug adherence and also tries to seek viewpoints of the same issue from different angles with various mathematical models to computer simulations. The book presents essential methods and techniques for students who are interested in designing epidemiological models on HIV/AIDS. It also guides research scientists, working in the periphery of mathematical modeling, and helps them to explore a hypothetical method by examining its consequences in the form of a mathematical modelling and making some scientific predictions. The model equations, mathematical analysis and several numerical simulations that are...
Walz, Yvonne; Wegmann, Martin; Dech, Stefan; Vounatsou, Penelope; Poda, Jean-Noël; N'Goran, Eliézer K; Utzinger, Jürg; Raso, Giovanna
2015-11-01
Schistosomiasis is the most widespread water-based disease in sub-Saharan Africa. Transmission is governed by the spatial distribution of specific freshwater snails that act as intermediate hosts and human water contact patterns. Remote sensing data have been utilized for spatially explicit risk profiling of schistosomiasis. We investigated the potential of remote sensing to characterize habitat conditions of parasite and intermediate host snails and discuss the relevance for public health. We employed high-resolution remote sensing data, environmental field measurements, and ecological data to model environmental suitability for schistosomiasis-related parasite and snail species. The model was developed for Burkina Faso using a habitat suitability index (HSI). The plausibility of remote sensing habitat variables was validated using field measurements. The established model was transferred to different ecological settings in Côte d'Ivoire and validated against readily available survey data from school-aged children. Environmental suitability for schistosomiasis transmission was spatially delineated and quantified by seven habitat variables derived from remote sensing data. The strengths and weaknesses highlighted by the plausibility analysis showed that temporal dynamic water and vegetation measures were particularly useful to model parasite and snail habitat suitability, whereas the measurement of water surface temperature and topographic variables did not perform appropriately. The transferability of the model showed significant relations between the HSI and infection prevalence in study sites of Côte d'Ivoire. A predictive map of environmental suitability for schistosomiasis transmission can support measures to gain and sustain control. This is particularly relevant as emphasis is shifting from morbidity control to interrupting transmission. Further validation of our mechanistic model needs to be complemented by field data of parasite- and snail
International Nuclear Information System (INIS)
McFadden, J.H.; Paulsen, M.P.; Gose, G.C.
1981-01-01
A time dependent equation for the slip velocity in a two-phase flow condition has been incorporated into a developmental version of the RETRAN computer code. This model addition has been undertaken to remove a limitation in RETRAN-01 associated with the homogeneous equilibrium mixture model. In this paper, the development of the slip model is summarized and the corresponding constitutive equations are discussed. Comparisons of RETRAN analyses with steady-state void fraction data and data from the Semiscale S-02-6 small break test are also presented
Modeling Propellant Tank Dynamics
National Aeronautics and Space Administration — The main objective of my work will be to develop accurate models of self-pressurizing propellant tanks for use in designing hybrid rockets. The first key goal is to...
Almberg, Emily S.; Cross, Paul C.; Johnson, Christopher J.; Heisey, Dennis M.; Richards, Bryan J.
2011-01-01
Chronic wasting disease (CWD) is a fatal disease of deer, elk, and moose transmitted through direct, animal-to-animal contact, and indirectly, via environmental contamination. Considerable attention has been paid to modeling direct transmission, but despite the fact that CWD prions can remain infectious in the environment for years, relatively little information exists about the potential effects of indirect transmission on CWD dynamics. In the present study, we use simulation models to demonstrate how indirect transmission and the duration of environmental prion persistence may affect epidemics of CWD and populations of North American deer. Existing data from Colorado, Wyoming, and Wisconsin's CWD epidemics were used to define plausible short-term outcomes and associated parameter spaces. Resulting long-term outcomes range from relatively low disease prevalence and limited host-population decline to host-population collapse and extinction. Our models suggest that disease prevalence and the severity of population decline is driven by the duration that prions remain infectious in the environment. Despite relatively low epidemic growth rates, the basic reproductive number, R0, may be much larger than expected under the direct-transmission paradigm because the infectious period can vastly exceed the host's life span. High prion persistence is expected to lead to an increasing environmental pool of prions during the early phases (i.e. approximately during the first 50 years) of the epidemic. As a consequence, over this period of time, disease dynamics will become more heavily influenced by indirect transmission, which may explain some of the observed regional differences in age and sex-specific disease patterns. This suggests management interventions, such as culling or vaccination, will become increasingly less effective as CWD epidemics progress.
Lee, Elizabeth C; Kelly, Michael R; Ochocki, Brad M; Akinwumi, Segun M; Hamre, Karen E S; Tien, Joseph H; Eisenberg, Marisa C
2017-05-07
Mathematical models of cholera and waterborne disease vary widely in their structures, in terms of transmission pathways, loss of immunity, and a range of other features. These differences can affect model dynamics, with different models potentially yielding different predictions and parameter estimates from the same data. Given the increasing use of mathematical models to inform public health decision-making, it is important to assess model distinguishability (whether models can be distinguished based on fit to data) and inference robustness (whether inferences from the model are robust to realistic variations in model structure). In this paper, we examined the effects of uncertainty in model structure in the context of epidemic cholera, testing a range of models with differences in transmission and loss of immunity structure, based on known features of cholera epidemiology. We fit these models to simulated epidemic and long-term data, as well as data from the 2006 Angola epidemic. We evaluated model distinguishability based on fit to data, and whether the parameter values, model behavior, and forecasting ability can accurately be inferred from incidence data. In general, all models were able to successfully fit to all data sets, both real and simulated, regardless of whether the model generating the simulated data matched the fitted model. However, in the long-term data, the best model fits were achieved when the loss of immunity structures matched those of the model that simulated the data. Two parameters, one representing person-to-person transmission and the other representing the reporting rate, were accurately estimated across all models, while the remaining parameters showed broad variation across the different models and data sets. The basic reproduction number (R 0 ) was often poorly estimated even using the correct model, due to practical unidentifiability issues in the waterborne transmission pathway which were consistent across all models. Forecasting
Modelling parasite transmission in a grazing system: the importance of host behaviour and immunity.
Directory of Open Access Journals (Sweden)
Naomi J Fox
Full Text Available Parasitic helminths present one of the most pervasive challenges to grazing herbivores. Many macro-parasite transmission models focus on host physiological defence strategies, omitting more complex interactions between hosts and their environments. This work represents the first model that integrates both the behavioural and physiological elements of gastro-intestinal nematode transmission dynamics in a managed grazing system. A spatially explicit, individual-based, stochastic model is developed, that incorporates both the hosts' immunological responses to parasitism, and key grazing behaviours including faecal avoidance. The results demonstrate that grazing behaviour affects both the timing and intensity of parasite outbreaks, through generating spatial heterogeneity in parasite risk and nutritional resources, and changing the timing of exposure to the parasites' free-living stages. The influence of grazing behaviour varies with the host-parasite combination, dependent on the development times of different parasite species and variations in host immune response. Our outputs include the counterintuitive finding that under certain conditions perceived parasite avoidance behaviours (faecal avoidance can increase parasite risk, for certain host-parasite combinations. Through incorporating the two-way interaction between infection dynamics and grazing behaviour, the potential benefits of parasite-induced anorexia are also demonstrated. Hosts with phenotypic plasticity in grazing behaviour, that make grazing decisions dependent on current parasite burden, can reduce infection with minimal loss of intake over the grazing season. This paper explores how both host behaviours and immunity influence macro-parasite transmission in a spatially and temporally heterogeneous environment. The magnitude and timing of parasite outbreaks is influenced by host immunity and behaviour, and the interactions between them; the incorporation of both regulatory processes
Modelling group dynamic animal movement
DEFF Research Database (Denmark)
Langrock, Roland; Hopcraft, J. Grant C.; Blackwell, Paul G.
2014-01-01
makes its movement decisions relative to the group centroid. The basic idea is framed within the flexible class of hidden Markov models, extending previous work on modelling animal movement by means of multi-state random walks. While in simulation experiments parameter estimators exhibit some bias......, to date, practical statistical methods which can include group dynamics in animal movement models have been lacking. We consider a flexible modelling framework that distinguishes a group-level model, describing the movement of the group's centre, and an individual-level model, such that each individual......Group dynamic movement is a fundamental aspect of many species' movements. The need to adequately model individuals' interactions with other group members has been recognised, particularly in order to differentiate the role of social forces in individual movement from environmental factors. However...
Directory of Open Access Journals (Sweden)
T. Déirdre Hollingsworth
2015-03-01
Full Text Available Many of the challenges which face modellers of directly transmitted pathogens also arise when modelling the epidemiology of pathogens with indirect transmission – whether through environmental stages, vectors, intermediate hosts or multiple hosts. In particular, understanding the roles of different hosts, how to measure contact and infection patterns, heterogeneities in contact rates, and the dynamics close to elimination are all relevant challenges, regardless of the mode of transmission. However, there remain a number of challenges that are specific and unique to modelling vector-borne diseases and macroparasites. Moreover, many of the neglected tropical diseases which are currently targeted for control and elimination are vector-borne, macroparasitic, or both, and so this article includes challenges which will assist in accelerating the control of these high-burden diseases. Here, we discuss the challenges of indirect measures of infection in humans, whether through vectors or transmission life stages and in estimating the contribution of different host groups to transmission. We also discuss the issues of “evolution-proof” interventions against vector-borne disease.
Hollingsworth, T Déirdre; Pulliam, Juliet R C; Funk, Sebastian; Truscott, James E; Isham, Valerie; Lloyd, Alun L
2015-03-01
Many of the challenges which face modellers of directly transmitted pathogens also arise when modelling the epidemiology of pathogens with indirect transmission--whether through environmental stages, vectors, intermediate hosts or multiple hosts. In particular, understanding the roles of different hosts, how to measure contact and infection patterns, heterogeneities in contact rates, and the dynamics close to elimination are all relevant challenges, regardless of the mode of transmission. However, there remain a number of challenges that are specific and unique to modelling vector-borne diseases and macroparasites. Moreover, many of the neglected tropical diseases which are currently targeted for control and elimination are vector-borne, macroparasitic, or both, and so this article includes challenges which will assist in accelerating the control of these high-burden diseases. Here, we discuss the challenges of indirect measures of infection in humans, whether through vectors or transmission life stages and in estimating the contribution of different host groups to transmission. We also discuss the issues of "evolution-proof" interventions against vector-borne disease. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.
Percolation Model of Sensory Transmission and Loss of Consciousness Under General Anesthesia
Zhou, David W.; Mowrey, David D.; Tang, Pei; Xu, Yan
2015-09-01
Neurons communicate with each other dynamically; how such communications lead to consciousness remains unclear. Here, we present a theoretical model to understand the dynamic nature of sensory activity and information integration in a hierarchical network, in which edges are stochastically defined by a single parameter p representing the percolation probability of information transmission. We validate the model by comparing the transmitted and original signal distributions, and we show that a basic version of this model can reproduce key spectral features clinically observed in electroencephalographic recordings of transitions from conscious to unconscious brain activities during general anesthesia. As p decreases, a steep divergence of the transmitted signal from the original was observed, along with a loss of signal synchrony and a sharp increase in information entropy in a critical manner; this resembles the precipitous loss of consciousness during anesthesia. The model offers mechanistic insights into the emergence of information integration from a stochastic process, laying the foundation for understanding the origin of cognition.
A data-driven model for influenza transmission incorporating media effects.
Mitchell, Lewis; Ross, Joshua V
2016-10-01
Numerous studies have attempted to model the effect of mass media on the transmission of diseases such as influenza; however, quantitative data on media engagement has until recently been difficult to obtain. With the recent explosion of 'big data' coming from online social media and the like, large volumes of data on a population's engagement with mass media during an epidemic are becoming available to researchers. In this study, we combine an online dataset comprising millions of shared messages relating to influenza with traditional surveillance data on flu activity to suggest a functional form for the relationship between the two. Using this data, we present a simple deterministic model for influenza dynamics incorporating media effects, and show that such a model helps explain the dynamics of historical influenza outbreaks. Furthermore, through model selection we show that the proposed media function fits historical data better than other media functions proposed in earlier studies.
Contact tracing of tuberculosis: a systematic review of transmission modelling studies.
Directory of Open Access Journals (Sweden)
Matt Begun
Full Text Available The WHO recommended intervention of Directly Observed Treatment, Short-course (DOTS appears to have been less successful than expected in reducing the burden of TB in some high prevalence settings. One strategy for enhancing DOTS is incorporating active case-finding through screening contacts of TB patients as widely used in low-prevalence settings. Predictive models that incorporate population-level effects on transmission provide one means of predicting impacts of such interventions. We aim to identify all TB transmission modelling studies addressing contact tracing and to describe and critically assess their modelling assumptions, parameter choices and relevance to policy. We searched MEDLINE, SCOPUS, COMPENDEX, Google Scholar and Web of Science databases for relevant English language publications up to February 2012. Of the 1285 studies identified, only 5 studies met our inclusion criteria of models of TB transmission dynamics in human populations designed to incorporate contact tracing as an intervention. Detailed implementation of contact processes was only present in two studies, while only one study presented a model for a high prevalence, developing world setting. Some use of relevant data for parameter estimation was made in each study however validation of the predicted impact of interventions was not attempted in any of the studies. Despite a large body of literature on TB transmission modelling, few published studies incorporate contact tracing. There is considerable scope for future analyses to make better use of data and to apply individual based models to facilitate more realistic patterns of infectious contact. Combined with a focus on high burden settings this would greatly increase the potential for models to inform the use of contract tracing as a TB control policy. Our findings highlight the potential for collaborative work between clinicians, epidemiologists and modellers to gather data required to enhance model development
Contact tracing of tuberculosis: a systematic review of transmission modelling studies.
Begun, Matt; Newall, Anthony T; Marks, Guy B; Wood, James G
2013-01-01
The WHO recommended intervention of Directly Observed Treatment, Short-course (DOTS) appears to have been less successful than expected in reducing the burden of TB in some high prevalence settings. One strategy for enhancing DOTS is incorporating active case-finding through screening contacts of TB patients as widely used in low-prevalence settings. Predictive models that incorporate population-level effects on transmission provide one means of predicting impacts of such interventions. We aim to identify all TB transmission modelling studies addressing contact tracing and to describe and critically assess their modelling assumptions, parameter choices and relevance to policy. We searched MEDLINE, SCOPUS, COMPENDEX, Google Scholar and Web of Science databases for relevant English language publications up to February 2012. Of the 1285 studies identified, only 5 studies met our inclusion criteria of models of TB transmission dynamics in human populations designed to incorporate contact tracing as an intervention. Detailed implementation of contact processes was only present in two studies, while only one study presented a model for a high prevalence, developing world setting. Some use of relevant data for parameter estimation was made in each study however validation of the predicted impact of interventions was not attempted in any of the studies. Despite a large body of literature on TB transmission modelling, few published studies incorporate contact tracing. There is considerable scope for future analyses to make better use of data and to apply individual based models to facilitate more realistic patterns of infectious contact. Combined with a focus on high burden settings this would greatly increase the potential for models to inform the use of contract tracing as a TB control policy. Our findings highlight the potential for collaborative work between clinicians, epidemiologists and modellers to gather data required to enhance model development and validation and
Modeling Internet Topology Dynamics
Haddadi, H.; Uhlig, S.; Moore, A.; Mortier, R.; Rio, M.
Despite the large number of papers on network topology modeling and inference, there still exists ambiguity about the real nature of the Internet AS and router level topology. While recent findings have illustrated the inaccuracies in maps inferred from BGP peering and traceroute measurements,
Generative Models of Conformational Dynamics
Langmead, Christopher James
2014-01-01
Atomistic simulations of the conformational dynamics of proteins can be performed using either Molecular Dynamics or Monte Carlo procedures. The ensembles of three-dimensional structures produced during simulation can be analyzed in a number of ways to elucidate the thermodynamic and kinetic properties of the system. The goal of this chapter is to review both traditional and emerging methods for learning generative models from atomistic simulation data. Here, the term ‘generative’ refers to a...
Theory and Circuit Model for Lossy Coaxial Transmission Line
Energy Technology Data Exchange (ETDEWEB)
Genoni, T. C.; Anderson, C. N.; Clark, R. E.; Gansz-Torres, J.; Rose, D. V.; Welch, Dale Robert
2017-04-01
The theory of signal propagation in lossy coaxial transmission lines is revisited and new approximate analytic formulas for the line impedance and attenuation are derived. The accuracy of these formulas from DC to 100 GHz is demonstrated by comparison to numerical solutions of the exact field equations. Based on this analysis, a new circuit model is described which accurately reproduces the line response over the entire frequency range. Circuit model calculations are in excellent agreement with the numerical and analytic results, and with finite-difference-time-domain simulations which resolve the skindepths of the conducting walls.
Phase space model for transmission of light beam
International Nuclear Information System (INIS)
Fu Shinian
1989-01-01
Based on Fermat's principle of ray optics, the Hamiltonian of an optical ray is derived by comparison with classical mechanics. A phase space model of light beam is proposed, assuming that the light beam, regarded as a group of rays, can be described by an ellipse in the μ-phase space. Therefore, the transmission of light beam is represented by the phase space matrix transformation. By means of this non-wave formulation, the same results are obtained as those from wave equation such as Kogelnik's ABCD law. As an example of the application on this model, the matching problem of optical cavity is solved
Energy Technology Data Exchange (ETDEWEB)
NONE
1995-02-17
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of integrated Analysis and Forecasting of the Energy information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. The NGTDM is the model within the NEMS that represents the transmission, distribution, and pricing of natural gas. The model also includes representations of the end-use demand for natural gas, the production of domestic natural gas, and the availability of natural gas traded on the international market based on information received from other NEMS models. The NGTDM determines the flow of natural gas in an aggregate, domestic pipeline network, connecting domestic and foreign supply regions with 12 demand regions. The methodology employed allows the analysis of impacts of regional capacity constraints in the interstate natural gas pipeline network and the identification of pipeline capacity expansion requirements. There is an explicit representation of core and noncore markets for natural gas transmission and distribution services, and the key components of pipeline tariffs are represented in a pricing algorithm. Natural gas pricing and flow patterns are derived by obtaining a market equilibrium across the three main elements of the natural gas market: the supply element, the demand element, and the transmission and distribution network that links them. The NGTDM consists of four modules: the Annual Flow Module, the Capacity F-expansion Module, the Pipeline Tariff Module, and the Distributor Tariff Module. A model abstract is provided in Appendix A.
International Nuclear Information System (INIS)
1995-01-01
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of integrated Analysis and Forecasting of the Energy information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. The NGTDM is the model within the NEMS that represents the transmission, distribution, and pricing of natural gas. The model also includes representations of the end-use demand for natural gas, the production of domestic natural gas, and the availability of natural gas traded on the international market based on information received from other NEMS models. The NGTDM determines the flow of natural gas in an aggregate, domestic pipeline network, connecting domestic and foreign supply regions with 12 demand regions. The methodology employed allows the analysis of impacts of regional capacity constraints in the interstate natural gas pipeline network and the identification of pipeline capacity expansion requirements. There is an explicit representation of core and noncore markets for natural gas transmission and distribution services, and the key components of pipeline tariffs are represented in a pricing algorithm. Natural gas pricing and flow patterns are derived by obtaining a market equilibrium across the three main elements of the natural gas market: the supply element, the demand element, and the transmission and distribution network that links them. The NGTDM consists of four modules: the Annual Flow Module, the Capacity F-expansion Module, the Pipeline Tariff Module, and the Distributor Tariff Module. A model abstract is provided in Appendix A
MONETARY POLICY TRANSMISSION MECHANISM AND TVP-VAR MODEL
Directory of Open Access Journals (Sweden)
Andreea ROŞOIU
2013-12-01
Full Text Available The transmission of monetary policy to the economy is a subject of major importance for central banks because, by using these measures, central banks can achieve their purpose of ensuring price stability without neglecting the objective of sustainable economic growth. In order to analyze the evolution of the monetary policy transmission mechanism in Romania, a time varying structural vector autoregression model is estimated, by using a Markov Chain Monte Carlo algorithm for the posterior evolution. The conclusions of the empirical study are: both systematic and non-systematic monetary policy have changed during the investigated period of time, the systematic response of the interest rate to shocks in inflation and unemployment being faster over the recent period. Also, non-policy shocks seem more important than interest rate shocks in explaining inflation and unemployment evolution.
Conlan, James V; Vongxay, Khamphouth; Fenwick, Stanley; Blacksell, Stuart D; Thompson, R C Andrew
2009-09-01
It is well understood that sociocultural practices strongly influence Taenia solium transmission; however, the extent to which interspecific parasite competition moderates Taenia transmission has yet to be determined. This is certainly the case in Southeast Asia where T. solium faces competition in both the definitive host (people) and the intermediate host (pigs). In people, adult worms of T. solium, T. saginata and T. asiatica compete through density-dependent crowding mechanisms. In pigs, metacestodes of T. solium, T. hydatigena and T. asiatica compete through density-dependent immune-mediated interactions. Here, we describe the biological and epidemiological implications of Taenia competition and propose that interspecific competition has a moderating effect on the transmission dynamics of T. solium in the region. Furthermore, we argue that this competitive ecological scenario should be considered in future research and surveillance activities examining T. solium cysticercosis and taeniasis in Southeast Asia.
International Nuclear Information System (INIS)
Foroud, Asghar Akbari; Abdoos, Ali Akbar; Keypour, Reza; Amirahmadi, Meisam
2010-01-01
Restructuring of power system has changed the traditional planning objectives and introduced challenges in the field of Transmission Expansion Planning (TEP). Due to these changes, new approaches and criteria are needed for transmission planning in deregulated environment. Therefore, in this paper, a dynamic expansion methodology is presented using a multi-objective optimization framework. Investment cost, congestion cost and reliability are considered in the optimization as three objectives. To overcome the difficulties in solving the non-convex and mixed integer nature of the optimization problems, a Non-Dominated Sorting Genetic Algorithm (NSGA II) approach is used followed by a fuzzy decision making analysis to obtain the final optimal solution. The planning methodology has been demonstrated on the IEEE 24-bus test system and north-east of Iran national 400 kV transmission grid to show the feasibility and capabilities of the proposed algorithm in electricity market environment. (author)
Mathematical modeling of agricultural fires beneath high voltage transmission lines
International Nuclear Information System (INIS)
El-Zohri, Emad H.; Shafey, Hamdy M.; Abdel-Salam, M.; Ahmed, A.
2011-01-01
This paper presents a mathematical model for agricultural fires based on a multi-phase formulation. The model includes dehydration and pyrolysis of agricultural fuel and pyrolysis products. The model considers a homogeneous distribution of the agricultural solid fuel particles, interacting with the gas flow via source terms. These terms include: drag forces, production of water vapour and pyrolysis products, radiative and convective heat exchange. A multi-phase radiative transfer equation for absorbing-emitting medium is considered to account for the radiative heat exchange between the gas and solid phases of the fire. The main outputs of the present model are most important to study the influence of agricultural fire occurring beneath high voltage transmission lines. The agricultural fire causes a flashover due to the ambient temperature rise and soot accumulation on the insulator of these transmission lines. Numerical results of the present model are obtained for flat grassland fires to study the effects of wind velocity, solid fuel moisture content and ignition length on some selected fire outputs. These outputs include the temperature, velocity, soot volume fraction fields of the gas phase, together with fire propagation rate and flame geometry. The numerical results are compared to the available experimental work in the literature. -- Research highlights: → The model is sensitive to the initial condition of the ignition length affecting the fire propagation rate and width. → The model predicts the effects of both the wind velocity and the fuel moisture content on fire propagation rate, in agreement with the available experimental work in the literature. → The model shows that both the wind velocity and the fuel moisture content are important factors affecting the fire plume thickness, location, and inclination. → The model is able to visualize the flame geometry through tracing radiative heat rates exceeding a threshold value for flame visibility (60 k
Vehicle dynamics modeling and simulation
Schramm, Dieter; Bardini, Roberto
2014-01-01
The authors examine in detail the fundamentals and mathematical descriptions of the dynamics of automobiles. In this context different levels of complexity will be presented, starting with basic single-track models up to complex three-dimensional multi-body models. A particular focus is on the process of establishing mathematical models on the basis of real cars and the validation of simulation results. The methods presented are explained in detail by means of selected application scenarios.
Kamath, Pauline L.; Foster, Jeffrey T.; Drees, Kevin P.; Luikart, Gordon; Quance, Christine; Anderson, Neil J.; Clarke, P. Ryan; Cole, Eric K.; Drew, Mark L.; Edwards, William H.; Rhyan, Jack C.; Treanor, John J.; Wallen, Rick L.; White, Patrick J.; Robbe-Austerman, Suelee; Cross, Paul C.
2016-01-01
Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (B3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations.
Containing Terrorism: A Dynamic Model
Directory of Open Access Journals (Sweden)
Giti Zahedzadeh
2017-06-01
Full Text Available The strategic interplay between counterterror measures and terror activity is complex. Herein, we propose a dynamic model to depict this interaction. The model generates stylized prognoses: (i under conditions of inefficient counterterror measures, terror groups enjoy longer period of activity but only if recruitment into terror groups remains low; high recruitment shortens the period of terror activity (ii highly efficient counterterror measures effectively contain terror activity, but only if recruitment remains low. Thus, highly efficient counterterror measures can effectively contain terrorism if recruitment remains restrained. We conclude that the trajectory of the dynamics between counterterror measures and terror activity is heavily altered by recruitment.
Guo, Dongmin; Li, King C; Peters, Timothy R; Snively, Beverly M; Poehling, Katherine A; Zhou, Xiaobo
2015-03-11
Mathematical modeling of influenza epidemic is important for analyzing the main cause of the epidemic and finding effective interventions towards it. The epidemic is a dynamic process. In this process, daily infections are caused by people's contacts, and the frequency of contacts can be mainly influenced by their cognition to the disease. The cognition is in turn influenced by daily illness attack rate, climate, and other environment factors. Few existing methods considered the dynamic process in their models. Therefore, their prediction results can hardly be explained by the mechanisms of epidemic spreading. In this paper, we developed a heterogeneous graph modeling approach (HGM) to describe the dynamic process of influenza virus transmission by taking advantage of our unique clinical data. We built social network of studied region and embedded an Agent-Based Model (ABM) in the HGM to describe the dynamic change of an epidemic. Our simulations have a good agreement with clinical data. Parameter sensitivity analysis showed that temperature influences the dynamic of epidemic significantly and system behavior analysis showed social network degree is a critical factor determining the size of an epidemic. Finally, multiple scenarios for vaccination and school closure strategies were simulated and their performance was analyzed.
Directory of Open Access Journals (Sweden)
Gina Polo
2017-06-01
Full Text Available Brazilian Spotted Fever (BSF, caused by the bacterium Rickettsia rickettsii, is the tick-borne disease that generates the largest number of human deaths in the world. In Brazil, the current increase of BSF human cases has been associated with the presence and expansion of capybaras Hydrochoerus hydrochaeris, which act as primary hosts for the tick Amblyomma sculptum, vector of the R. rickettsii in this area.We proposed a semi-discrete-time stochastic model to evaluate the role of capybaras in the transmission dynamics of R. rickettsii. Through a sensitivity analysis, we identified the parameters with significant influence on the R. rickettsii establishment. Afterward, we implemented the Gillespie's algorithm to simulate the impact of potential public health interventions to prevent BSF human cases.The introduction of a single infected capybara with at least one infected attached tick is enough to trigger the disease in a non-endemic area. We found that to avoid the formation of new BSF-endemic areas, it is crucial to impede the emigration of capybaras from endemic areas by reducing their birth rate by more than 58%. Model results were corroborated by ex-situ data generated from field studies, and this supports our proposal to prevent BSF human cases by implementing control strategies focused on capybaras.The proposed stochastic model illustrates how strategies for the control and prevention of vector-borne infectious diseases can be focused on amplifier hosts management practices. This work provides a basis for future prevention strategies for other neglected vector-borne diseases.
Mahmud, A. S.; Metcalf, C. J. E.; Grenfell, B. T.
2018-01-01
The seasonality and periodicity of infections, and the mechanisms underlying observed dynamics, can have implications for control efforts. This is particularly true for acute childhood infections. Among these, the dynamics of measles is the best understood and has been extensively studied, most notably in the UK prior to the start of vaccination. Less is known about the dynamics of other childhood diseases, particularly outside Europe and the US. In this paper, we leverage a unique dataset to examine the epidemiology of six childhood infections - measles, mumps, rubella, varicella, scarlet fever and pertussis - across 32 states in Mexico from 1985 to 2007. This dataset provides us with a spatiotemporal probe into the dynamics of six common childhood infections, and allows us to compare them in the same setting over the same time period. We examine three key epidemiological characteristics of these infections – the age profile of infections, spatiotemporal dynamics, and seasonality in transmission - and compare with predictions from existing theory and past findings. Our analysis reveals interesting epidemiological differences between the six pathogens, and variations across space. We find signatures of term time forcing (reduced transmission during the summer) for measles, mumps, rubella, varicella, and scarlet fever; for pertussis, a lack of term time forcing could not be rejected. PMID:27873563
A dynamical model of terrorism
Directory of Open Access Journals (Sweden)
Firdaus Udwadia
2006-01-01
Full Text Available This paper develops a dynamical model of terrorism. We consider the population in a given region as being made up of three primary components: terrorists, those susceptible to both terrorist and pacifist propaganda, and nonsusceptibles, or pacifists. The dynamical behavior of these three populations is studied using a model that incorporates the effects of both direct military/police intervention to reduce the terrorist population, and nonviolent, persuasive intervention to influence the susceptibles to become pacifists. The paper proposes a new paradigm for studying terrorism, and looks at the long-term dynamical evolution in time of these three population components when such interventions are carried out. Many important features—some intuitive, others not nearly so—of the nature of terrorism emerge from the dynamical model proposed, and they lead to several important policy implications for the management of terrorism. The different circumstances in which nonviolent intervention and/or military/police intervention may be beneficial, and the specific conditions under which each mode of intervention, or a combination of both, may be useful, are obtained. The novelty of the model presented herein is that it deals with the time evolution of terrorist activity. It appears to be one of the few models that can be tested, evaluated, and improved upon, through the use of actual field data.
Generative Models of Conformational Dynamics
Langmead, Christopher James
2014-01-01
Atomistic simulations of the conformational dynamics of proteins can be performed using either Molecular Dynamics or Monte Carlo procedures. The ensembles of three-dimensional structures produced during simulation can be analyzed in a number of ways to elucidate the thermodynamic and kinetic properties of the system. The goal of this chapter is to review both traditional and emerging methods for learning generative models from atomistic simulation data. Here, the term ‘generative’ refers to a model of the joint probability distribution over the behaviors of the constituent atoms. In the context of molecular modeling, generative models reveal the correlation structure between the atoms, and may be used to predict how the system will respond to structural perturbations. We begin by discussing traditional methods, which produce multivariate Gaussian models. We then discuss GAMELAN (GrAphical Models of Energy LANdscapes), which produces generative models of complex, non-Gaussian conformational dynamics (e.g., allostery, binding, folding, etc) from long timescale simulation data. PMID:24446358
Dynamic modeling of gearbox faults: A review
Liang, Xihui; Zuo, Ming J.; Feng, Zhipeng
2018-01-01
Gearbox is widely used in industrial and military applications. Due to high service load, harsh operating conditions or inevitable fatigue, faults may develop in gears. If the gear faults cannot be detected early, the health will continue to degrade, perhaps causing heavy economic loss or even catastrophe. Early fault detection and diagnosis allows properly scheduled shutdowns to prevent catastrophic failure and consequently result in a safer operation and higher cost reduction. Recently, many studies have been done to develop gearbox dynamic models with faults aiming to understand gear fault generation mechanism and then develop effective fault detection and diagnosis methods. This paper focuses on dynamics based gearbox fault modeling, detection and diagnosis. State-of-art and challenges are reviewed and discussed. This detailed literature review limits research results to the following fundamental yet key aspects: gear mesh stiffness evaluation, gearbox damage modeling and fault diagnosis techniques, gearbox transmission path modeling and method validation. In the end, a summary and some research prospects are presented.
Experimental Modeling of Dynamic Systems
DEFF Research Database (Denmark)
Knudsen, Morten Haack
2006-01-01
An engineering course, Simulation and Experimental Modeling, has been developed that is based on a method for direct estimation of physical parameters in dynamic systems. Compared with classical system identification, the method appears to be easier to understand, apply, and combine with physical...
Lyapunov functions for a dengue disease transmission model
International Nuclear Information System (INIS)
Tewa, Jean Jules; Dimi, Jean Luc; Bowong, Samuel
2009-01-01
In this paper, we study a model for the dynamics of dengue fever when only one type of virus is present. For this model, Lyapunov functions are used to show that when the basic reproduction ratio is less than or equal to one, the disease-free equilibrium is globally asymptotically stable, and when it is greater than one there is an endemic equilibrium which is also globally asymptotically stable.
Lyapunov functions for a dengue disease transmission model
Energy Technology Data Exchange (ETDEWEB)
Tewa, Jean Jules [Department of Mathematics, Faculty of Science, University of Yaounde I, P.O. Box 812, Yaounde (Cameroon)], E-mail: tewa@univ-metz.fr; Dimi, Jean Luc [Department of Mathematics, Faculty of Science, University Marien Ngouabi, P.O. Box 69, Brazzaville (Congo, The Democratic Republic of the)], E-mail: jldimi@yahoo.fr; Bowong, Samuel [Department of Mathematics and Computer Science, Faculty of Science, University of Douala, P.O. Box 24157, Douala (Cameroon)], E-mail: samuelbowong@yahoo.fr
2009-01-30
In this paper, we study a model for the dynamics of dengue fever when only one type of virus is present. For this model, Lyapunov functions are used to show that when the basic reproduction ratio is less than or equal to one, the disease-free equilibrium is globally asymptotically stable, and when it is greater than one there is an endemic equilibrium which is also globally asymptotically stable.
Optimizing agent-based transmission models for infectious diseases.
Willem, Lander; Stijven, Sean; Tijskens, Engelbert; Beutels, Philippe; Hens, Niel; Broeckhove, Jan
2015-06-02
Infectious disease modeling and computational power have evolved such that large-scale agent-based models (ABMs) have become feasible. However, the increasing hardware complexity requires adapted software designs to achieve the full potential of current high-performance workstations. We have found large performance differences with a discrete-time ABM for close-contact disease transmission due to data locality. Sorting the population according to the social contact clusters reduced simulation time by a factor of two. Data locality and model performance can also be improved by storing person attributes separately instead of using person objects. Next, decreasing the number of operations by sorting people by health status before processing disease transmission has also a large impact on model performance. Depending of the clinical attack rate, target population and computer hardware, the introduction of the sort phase decreased the run time from 26% up to more than 70%. We have investigated the application of parallel programming techniques and found that the speedup is significant but it drops quickly with the number of cores. We observed that the effect of scheduling and workload chunk size is model specific and can make a large difference. Investment in performance optimization of ABM simulator code can lead to significant run time reductions. The key steps are straightforward: the data structure for the population and sorting people on health status before effecting disease propagation. We believe these conclusions to be valid for a wide range of infectious disease ABMs. We recommend that future studies evaluate the impact of data management, algorithmic procedures and parallelization on model performance.
Mehta, Sanjay R; Chaillon, Antoine; Gaines, Tommi L; Gonzalez-Zuniga, Patricia E; Stockman, Jamila K; Almanza-Reyes, Horatio; Chavez, Jose Roman; Vera, Alicia; Wagner, Karla D; Patterson, Thomas L; Scott, Brianna; Smith, Davey M; Strathdee, Steffanie A
2018-02-10
North Tijuana, Mexico is home to many individuals at high risk for transmitting and acquiring human immunodeficiency virus (HIV). Recently, policy shifts by local government impacted how these individuals were handled by authorities. Here we examined how this affected regional HIV transmission dynamics. HIV pol sequences and associated demographic information were collected from 8 research studies enrolling persons in Tijuana and were used to infer viral transmission patterns. To evaluate the impact of recent policy changes on HIV transmission dynamics, qualitative interviews were performed on a subset of recently infected individuals. Between 2004 and 2016, 288 unique HIV pol sequences were obtained from individuals in Tijuana, including 46.4% from men who have sex with men, 42.1% from individuals reporting transactional sex, and 27.8% from persons who inject drugs (some individuals had >1 risk factor). Forty-two percent of sequences linked to at least 1 other sequence, forming 37 transmission clusters. Thirty-two individuals seroconverted during the observation period, including 8 between April and July 2016. Three of these individuals were putatively linked together. Qualitative interviews suggested changes in policing led individuals to shift locations of residence and injection drug use, leading to increased risk taking (eg, sharing needles). Near real-time molecular epidemiologic analyses identified a cluster of linked transmissions temporally associated with policy shifts. Interviews suggested these shifts may have led to increased risk taking among individuals at high risk for HIV acquisition. With all public policy shifts, downstream impacts need to be carefully considered, as even well-intentioned policies can have major public health consequences. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.
Control-Oriented Models for Real-Time Simulation of Automotive Transmission Systems
Directory of Open Access Journals (Sweden)
Cavina N.
2015-01-01
Full Text Available A control-oriented model of a Dual Clutch Transmission (DCT was developed for real-time Hardware In the Loop (HIL applications, to support model-based development of the DCT controller and to systematically test its performance. The model is an innovative attempt to reproduce the fast dynamics of the actuation system while maintaining a simulation step size large enough for real-time applications. The model comprehends a detailed physical description of hydraulic circuit, clutches, synchronizers and gears, and simplified vehicle and internal combustion engine sub-models. As the oil circulating in the system has a large bulk modulus, the pressure dynamics are very fast, possibly causing instability in a real-time simulation; the same challenge involves the servo valves dynamics, due to the very small masses of the moving elements. Therefore, the hydraulic circuit model has been modified and simplified without losing physical validity, in order to adapt it to the real-time simulation requirements. The results of offline simulations have been compared to on-board measurements to verify the validity of the developed model, which was then implemented in a HIL system and connected to the Transmission Control Unit (TCU. Several tests have been performed on the HIL simulator, to verify the TCU performance: electrical failure tests on sensors and actuators, hydraulic and mechanical failure tests on hydraulic valves, clutches and synchronizers, and application tests comprehending all the main features of the control actions performed by the TCU. Being based on physical laws, in every condition the model simulates a plausible reaction of the system. A test automation procedure has finally been developed to permit the execution of a pattern of tests without the interaction of the user; perfectly repeatable tests can be performed for non-regression verification, allowing the testing of new software releases in fully automatic mode.
Malaria transmission dynamics at a site in northern Ghana proposed for testing malaria vaccines.
Appawu, Maxwell; Owusu-Agyei, Seth; Dadzie, Samuel; Asoala, Victor; Anto, Francis; Koram, Kwadwo; Rogers, William; Nkrumah, Francis; Hoffman, Stephen L; Fryauff, David J
2004-01-01
We studied the malaria transmission dynamics in Kassena Nankana district (KND), a site in northern Ghana proposed for testing malaria vaccines. Intensive mosquito sampling for 1 year using human landing catches in three micro-ecological sites (irrigated, lowland and rocky highland) yielded 18 228 mosquitoes. Anopheles gambiae s.l. and Anopheles funestus constituted 94.3% of the total collection with 76.8% captured from the irrigated communities. Other species collected but in relatively few numbers were Anopheles pharoensis (5.4%) and Anopheles rufipes (0.3%). Molecular analysis of 728 An. gambiae.s.l. identified Anopheles gambiae s.s. as the most dominant sibling species (97.7%) of the An. gambiae complex from the three ecological sites. Biting rates of the vectors (36.7 bites per man per night) were significantly higher (P<0.05) in the irrigated area than in the non-irrigated lowland (5.2) and rocky highlands (5.9). Plasmodium falciparum sporozoite rates of 7.2% (295/4075) and 7.1% (269/3773) were estimated for An. gambiae s.s. and An. funestus, respectively. Transmission was highly seasonal, and the heaviest transmission occurred from June to October. The intensity of transmission was higher for people in the irrigated communities than the non-irrigated ones. An overall annual entomological inoculation rate (EIR) of 418 infective bites was estimated in KND. There were micro-ecological variations in the EIRs, with values of 228 infective bites in the rocky highlands, 360 in the lowlands and 630 in the irrigated area. Approximately 60% of malaria transmission in KND occurred indoors during the second half of the night, peaking at daybreak between 04.00 and 06.00 hours. Vaccine trials could be conducted in this district, with timing dependent on the seasonal patterns and intensity of transmission taking into consideration the micro-geographical differences and vaccine trial objectives.
Directory of Open Access Journals (Sweden)
Diana Tilevik
2016-05-01
Full Text Available Background: The increasing prevalence of penicillin non-susceptible pneumococci (PNSP throughout the world threatens successful treatment of infections caused by this important bacterial pathogen. The rate at which PNSP clones spread in the community is thought to mainly be determined by two key determinants; the volume of penicillin use and the magnitude of the fitness cost in the absence of treatment. The aim of the study was to determine the impacts of penicillin consumption and fitness cost on pneumococcal transmission dynamics in a developed country setting. Methods: An individual-based network model based on real-life demographic data was constructed and applied in a developed country setting (Sweden. A population structure with transmission of carriage taking place within relevant mixing groups, i.e. families, day care groups, school classes, and other close contacts, was considered to properly assess the transmission dynamics for susceptible and PNSP clones. Several scenarios were simulated and model outcomes were statistically analysed. Results: Model simulations predicted that with an outpatient penicillin use corresponding to the sales in Sweden 2010 (118 recipes per 1,000 inhabitants per year, the magnitude of a fitness cost for resistance must be at least 5% to offset the advantage of penicillin resistance. Moreover, even if there is a fitness cost associated with penicillin resistance, a considerable reduction of penicillin usage appears to be required to significantly decrease the incidence of PNSP in a community. Conclusion: The frequency of PNSP clones is hard to reverse by simply reducing the penicillin consumption even if there is a biological cost associated with resistance. However, because penicillin usage does promote further spread of PNSP clones, it is important to keep down penicillin consumption considering future resistance problems.
Directory of Open Access Journals (Sweden)
Xinlei Liu
2012-08-01
Full Text Available On the basis of the shifting process of automated mechanical transmissions (AMTs for traditional hybrid electric vehicles (HEVs, and by combining the features of electric machines with fast response speed, the dynamic model of the hybrid electric AMT vehicle powertrain is built up, the dynamic characteristics of each phase of shifting process are analyzed, and a control strategy in which torque and speed of the engine and electric machine are coordinatively controlled to achieve AMT shifting control for a plug-in hybrid electric vehicle (PHEV without clutch is proposed. In the shifting process, the engine and electric machine are well controlled, and the shift jerk and power interruption and restoration time are reduced. Simulation and real car test results show that the proposed control strategy can more efficiently improve the shift quality for PHEVs equipped with AMTs.
Pollutant Dispersion Modeling in Natural Streams Using the Transmission Line Matrix Method
Directory of Open Access Journals (Sweden)
Safia Meddah
2015-09-01
Full Text Available Numerical modeling has become an indispensable tool for solving various physical problems. In this context, we present a model of pollutant dispersion in natural streams for the far field case where dispersion is considered longitudinal and one-dimensional in the flow direction. The Transmission Line Matrix (TLM, which has earned a reputation as powerful and efficient numerical method, is used. The presented one-dimensional TLM model requires a minimum input data and provides a significant gain in computing time. To validate our model, the results are compared with observations and experimental data from the river Severn (UK. The results show a good agreement with experimental data. The model can be used to predict the spatiotemporal evolution of a pollutant in natural streams for effective and rapid decision-making in a case of emergency, such as accidental discharges in a stream with a dynamic similar to that of the river Severn (UK.
Transmission Delay Modeling of Packet Communication over Digital Subscriber Line
Directory of Open Access Journals (Sweden)
Jiri Vodrazka
2013-01-01
Full Text Available Certain multimedia and voice services, such as VoIP, IPTV, etc., are significantly delay sensitive and their performance is influenced by the overall transmission delay and its variance. One of the most common solutions used in access networks are xDSL lines, especially ADSL2+ or VDSL2. Although these subscriber lines also use packet communication, there are several differences and mechanisms, which influence their resulting delay. Their delay characteristics are also dependent on the individual settings of each xDSL provider, therefore we decided to investigate this area for typical commercially available lines in Czech Republic. Based on the measured values and experiments with real ADSL2+ lines we also developed a potential modeling method, which is presented in this article as well. The parameters for packet jitter based on the generalized Pareto distribution were modeled.
Business model dynamics and innovation
DEFF Research Database (Denmark)
Cavalcante, Sergio Andre; Kesting, Peter; Ulhøi, John Parm
2011-01-01
the impact of specific changes to a firm's business model. Such a tool would be particularly useful in identifying path dependencies and resistance at the process level, and would therefore allow a firm's management to take focused action on this in advance. Originality/value – The paper makes two main...... and specifies four different types of business model change: business model creation, extension, revision, and termination. Each type of business model change is associated with specific challenges. Practical implications – The proposed typology can serve as a basis for developing a management tool to evaluate......Purpose – This paper aims to discuss the need to dynamize the existing conceptualization of business model, and proposes a new typology to distinguish different types of business model change. Design/methodology/approach – The paper integrates basic insights of innovation, business process...
On whole Abelian model dynamics
Energy Technology Data Exchange (ETDEWEB)
Chauca, J.; Doria, R. [CBPF, Rio de Janeiro (Brazil); Aprendanet, Petropolis, 25600 (Brazil)
2012-09-24
Physics challenge is to determine the objects dynamics. However, there are two ways for deciphering the part. The first one is to search for the ultimate constituents; the second one is to understand its behaviour in whole terms. Therefore, the parts can be defined either from elementary constituents or as whole functions. Historically, science has been moving through the first aspect, however, quarks confinement and complexity are interrupting this usual approach. These relevant facts are supporting for a systemic vision be introduced. Our effort here is to study on the whole meaning through gauge theory. Consider a systemic dynamics oriented through the U(1) - systemic gauge parameter which function is to collect a fields set {l_brace}A{sub {mu}I}{r_brace}. Derive the corresponding whole gauge invariant Lagrangian, equations of motion, Bianchi identities, Noether relationships, charges and Ward-Takahashi equations. Whole Lorentz force and BRST symmetry are also studied. These expressions bring new interpretations further than the usual abelian model. They are generating a systemic system governed by 2N+ 10 classical equations plus Ward-Takahashi identities. A whole dynamics based on the notions of directive and circumstance is producing a set determinism where the parts dynamics are inserted in the whole evolution. A dynamics based on state, collective and individual equations with a systemic interdependence.
International Nuclear Information System (INIS)
1996-01-01
The Natural Gas Transmission and Distribution Model (NGTDM) of the National Energy Modeling System is developed and maintained by the Energy Information Administration (EIA), Office of Integrated Analysis and Forecasting. This report documents the archived version of the NGTDM that was used to produce the natural gas forecasts presented in the Annual Energy Outlook 1996, (DOE/EIA-0383(96)). The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic approach, and provides detail on the methodology employed. Previously this report represented Volume I of a two-volume set. Volume II reported on model performance, detailing convergence criteria and properties, results of sensitivity testing, comparison of model outputs with the literature and/or other model results, and major unresolved issues
Energy Technology Data Exchange (ETDEWEB)
NONE
1996-02-26
The Natural Gas Transmission and Distribution Model (NGTDM) of the National Energy Modeling System is developed and maintained by the Energy Information Administration (EIA), Office of Integrated Analysis and Forecasting. This report documents the archived version of the NGTDM that was used to produce the natural gas forecasts presented in the Annual Energy Outlook 1996, (DOE/EIA-0383(96)). The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic approach, and provides detail on the methodology employed. Previously this report represented Volume I of a two-volume set. Volume II reported on model performance, detailing convergence criteria and properties, results of sensitivity testing, comparison of model outputs with the literature and/or other model results, and major unresolved issues.
Relating structure and dynamics in organisation models
Jonkers, C.M.; Treur, J.
2002-01-01
To understand how an organisational structure relates to dynamics is an interesting fundamental challenge in the area of social modelling. Specifications of organisational structure usually have a diagrammatic form that abstracts from more detailed dynamics. Dynamic properties of agent systems,
Modelling MIZ dynamics in a global model
Rynders, Stefanie; Aksenov, Yevgeny; Feltham, Daniel; Nurser, George; Naveira Garabato, Alberto
2016-04-01
Exposure of large, previously ice-covered areas of the Arctic Ocean to the wind and surface ocean waves results in the Arctic pack ice cover becoming more fragmented and mobile, with large regions of ice cover evolving into the Marginal Ice Zone (MIZ). The need for better climate predictions, along with growing economic activity in the Polar Oceans, necessitates climate and forecasting models that can simulate fragmented sea ice with a greater fidelity. Current models are not fully fit for the purpose, since they neither model surface ocean waves in the MIZ, nor account for the effect of floe fragmentation on drag, nor include sea ice rheology that represents both the now thinner pack ice and MIZ ice dynamics. All these processes affect the momentum transfer to the ocean. We present initial results from a global ocean model NEMO (Nucleus for European Modelling of the Ocean) coupled to the Los Alamos sea ice model CICE. The model setup implements a novel rheological formulation for sea ice dynamics, accounting for ice floe collisions, thus offering a seamless framework for pack ice and MIZ simulations. The effect of surface waves on ice motion is included through wave pressure and the turbulent kinetic energy of ice floes. In the multidecadal model integrations we examine MIZ and basin scale sea ice and oceanic responses to the changes in ice dynamics. We analyse model sensitivities and attribute them to key sea ice and ocean dynamical mechanisms. The results suggest that the effect of the new ice rheology is confined to the MIZ. However with the current increase in summer MIZ area, which is projected to continue and may become the dominant type of sea ice in the Arctic, we argue that the effects of the combined sea ice rheology will be noticeable in large areas of the Arctic Ocean, affecting sea ice and ocean. With this study we assert that to make more accurate sea ice predictions in the changing Arctic, models need to include MIZ dynamics and physics.
A dynamic, climate-driven model of Rift Valley fever
Directory of Open Access Journals (Sweden)
Joseph Leedale
2016-03-01
Full Text Available Outbreaks of Rift Valley fever (RVF in eastern Africa have previously occurred following specific rainfall dynamics and flooding events that appear to support the emergence of large numbers of mosquito vectors. As such, transmission of the virus is considered to be sensitive to environmental conditions and therefore changes in climate can impact the spatiotemporal dynamics of epizootic vulnerability. Epidemiological information describing the methods and parameters of RVF transmission and its dependence on climatic factors are used to develop a new spatio-temporal mathematical model that simulates these dynamics and can predict the impact of changes in climate. The Liverpool RVF (LRVF model is a new dynamic, process-based model driven by climate data that provides a predictive output of geographical changes in RVF outbreak susceptibility as a result of the climate and local livestock immunity. This description of the multi-disciplinary process of model development is accessible to mathematicians, epidemiological modellers and climate scientists, uniting dynamic mathematical modelling, empirical parameterisation and state-of-the-art climate information.
Transmission dynamics of Schistosoma japonicum in the lakes and marshlands of China.
Directory of Open Access Journals (Sweden)
Darren J Gray
Full Text Available Schistosoma japonicum is a major public health concern in China, with over one million people infected and another 40 million living in areas at risk of infection. Unlike the disease caused by S. mansoni and S. haematobium, schistosomiasis japonica is a zoonosis, involving a number of different mammalian species as reservoir hosts. As a result of a number of published reports from China, it has long been considered that bovines, particularly water buffaloes, play a major role in human S. japonicum transmission there, and a drug-based intervention study (1998-2003 around the Poyang Lake in Jiangxi Province provided proof of concept that water buffaloes are, indeed, major reservoirs of human infection in this setting.In this study we incorporated recently obtained epidemiological information to model the steady-state S. japonicum transmission as well as the impact of the removal of S. japonicum transmission attributable to water buffaloes on human infection rates across six different endemic scenarios within three villages in the Dongting (Hunan and Poyang (Jiangxi lakes of southern China. Similar results were obtained for all scenarios. Steady-state S. japonicum infection rates remained constant and human prevalence and incidence were predicted to fall considerably over time. The model showed that the contribution of S. japonicum water buffalo transmission to human infection ranged from 39.1% to 99.1% and predicted that the removal of water buffalo transmission would reduce parasite reproductive rates below 1. This indicates that without the contribution of water buffaloes, S. japonicum transmission is interrupted and unsustainable. These scenarios are generalizable to other endemic villages in the lake and marshland areas of China where a similar cycle of snail infection and infection/reinfection of humans and bovines occurs.Along with previous epidemiological data, our findings strongly support water buffaloes as an important component of the
Miller, Eric L.; Dudenhoefer, James E.
1989-01-01
The signal distortion inherent to pressure transmission lines in free-piston Stirling engine research is discussed. Based on results from classical analysis, guidelines are formulated to describe the dynamic response properties of a volume-terminated transmission tube for applications involving the helium-charged free-piston Stirling engines. The underdamped flow regime is described, the primary resonance frequency is derived, and the pressure phase and amplitude distortion are discussed. The scope and limitation of the dynamic response analysis are considered.
Nonlinear dynamics of avian influenza epidemic models.
Liu, Sanhong; Ruan, Shigui; Zhang, Xinan
2017-01-01
Avian influenza is a zoonotic disease caused by the transmission of the avian influenza A virus, such as H5N1 and H7N9, from birds to humans. The avian influenza A H5N1 virus has caused more than 500 human infections worldwide with nearly a 60% death rate since it was first reported in Hong Kong in 1997. The four outbreaks of the avian influenza A H7N9 in China from March 2013 to June 2016 have resulted in 580 human cases including 202 deaths with a death rate of nearly 35%. In this paper, we construct two avian influenza bird-to-human transmission models with different growth laws of the avian population, one with logistic growth and the other with Allee effect, and analyze their dynamical behavior. We obtain a threshold value for the prevalence of avian influenza and investigate the local or global asymptotical stability of each equilibrium of these systems by using linear analysis technique or combining Liapunov function method and LaSalle's invariance principle, respectively. Moreover, we give necessary and sufficient conditions for the occurrence of periodic solutions in the avian influenza system with Allee effect of the avian population. Numerical simulations are also presented to illustrate the theoretical results. Copyright © 2016 Elsevier Inc. All rights reserved.
Directory of Open Access Journals (Sweden)
Eroboghene H Otete
Full Text Available INTRODUCTION: Mathematical modelling of Clostridium difficile infection dynamics could contribute to the optimisation of strategies for its prevention and control. The objective of this systematic review was to summarise the available literature specifically identifying the quantitative parameters required for a compartmental mathematical model of Clostridium difficile transmission. METHODS: Six electronic healthcare databases were searched and all screening, data extraction and study quality assessments were undertaken in duplicate. Results were synthesised using a narrative approach. RESULTS: Fifty-four studies met the inclusion criteria. Reproduction numbers for hospital based epidemics were described in two studies with a range from 0.55 to 7. Two studies provided consistent data on incubation periods. For 62% of cases, symptoms occurred in less than 4 weeks (3-28 days after infection. Evidence on contact patterns was identified in four studies but with limited data reported for populating a mathematical model. Two studies, including one without clinically apparent donor-recipient pairs, provided information on serial intervals for household or ward contacts, showing transmission intervals of <1 week in ward based contacts compared to up to 2 months for household contacts. Eight studies reported recovery rates of between 75%-100% for patients who had been treated with either metronidazole or vancomycin. Forty-nine studies gave recurrence rates of between 3% and 49% but were limited by varying definitions of recurrence. No study was found which specifically reported force of infection or net reproduction numbers. CONCLUSIONS: There is currently scant literature overtly citing estimates of the parameters required to inform the quantitative modelling of Clostridium difficile transmission. Further high quality studies to investigate transmission parameters are required, including through review of published epidemiological studies where these
Social Dynamics Modeling and Inference
2018-03-29
the experiment(s)/ theory and equipment or analyses. Development of innovative theoretical model and methodologies with experimental verifications...information. The methodology based on communication and information theory (thanks to leave at MIT supported by this research) is described in [J1], [C2...a dynamic system [C1] and as a social learning mechanism in details [J4]. Furthermore, by incentive seeding and rewiring connections, information
International Nuclear Information System (INIS)
Dinh, Minh-Chau; Ju, Chang-Hyeon; Kim, Sung-Kyu; Kim, Jin-Geun; Park, Minwon; Yu, In-Keun
2012-01-01
The combination of a high temperature superconducting DC power cable and a voltage source converter based HVDC (VSC-HVDC) creates a new option for transmitting power with multiple collection and distribution points for long distance and bulk power transmissions. It offers some greater advantages compared with HVAC or conventional HVDC transmission systems, and it is well suited for the grid integration of renewable energy sources in existing distribution or transmission systems. For this reason, a superconducting DC transmission system based HVDC transmission technologies is planned to be set up in the Jeju power system, Korea. Before applying this system to a real power system on Jeju Island, system analysis should be performed through a real time test. In this paper, a model-sized superconducting VSC-HVDC system, which consists of a small model-sized VSC-HVDC connected to a 2 m YBCO HTS DC model cable, is implemented. The authors have performed the real-time simulation method that incorporates the model-sized superconducting VSC-HVDC system into the simulated Jeju power system using Real Time Digital Simulator (RTDS). The performance analysis of the superconducting VSC-HVDC systems has been verified by the proposed test platform and the results were discussed in detail.
Energy Technology Data Exchange (ETDEWEB)
Dinh, Minh-Chau, E-mail: thanchau7787@gmail.com [Changwon National University, 9 Sarim-Dong, Changwon 641-733 (Korea, Republic of); Ju, Chang-Hyeon; Kim, Sung-Kyu; Kim, Jin-Geun; Park, Minwon [Changwon National University, 9 Sarim-Dong, Changwon 641-733 (Korea, Republic of); Yu, In-Keun, E-mail: yuik@changwon.ac.kr [Changwon National University, 9 Sarim-Dong, Changwon 641-733 (Korea, Republic of)
2012-08-15
The combination of a high temperature superconducting DC power cable and a voltage source converter based HVDC (VSC-HVDC) creates a new option for transmitting power with multiple collection and distribution points for long distance and bulk power transmissions. It offers some greater advantages compared with HVAC or conventional HVDC transmission systems, and it is well suited for the grid integration of renewable energy sources in existing distribution or transmission systems. For this reason, a superconducting DC transmission system based HVDC transmission technologies is planned to be set up in the Jeju power system, Korea. Before applying this system to a real power system on Jeju Island, system analysis should be performed through a real time test. In this paper, a model-sized superconducting VSC-HVDC system, which consists of a small model-sized VSC-HVDC connected to a 2 m YBCO HTS DC model cable, is implemented. The authors have performed the real-time simulation method that incorporates the model-sized superconducting VSC-HVDC system into the simulated Jeju power system using Real Time Digital Simulator (RTDS). The performance analysis of the superconducting VSC-HVDC systems has been verified by the proposed test platform and the results were discussed in detail.
International Nuclear Information System (INIS)
LaGrange, Thomas; Campbell, Geoffrey H.; Reed, B.W.; Taheri, Mitra; Pesavento, J. Bradley; Kim, Judy S.; Browning, Nigel D.
2008-01-01
Most biological processes, chemical reactions and materials dynamics occur at rates much faster than can be captured with standard video rate acquisition methods in transmission electron microscopes (TEM). Thus, there is a need to increase the temporal resolution in order to capture and understand salient features of these rapid materials processes. This paper details the development of a high-time resolution dynamic transmission electron microscope (DTEM) that captures dynamics in materials with nanosecond time resolution. The current DTEM performance, having a spatial resolution <10 nm for single-shot imaging using 15 ns electron pulses, will be discussed in the context of experimental investigations in solid state reactions of NiAl reactive multilayer films, the study of martensitic transformations in nanocrystalline Ti and the catalytic growth of Si nanowires. In addition, this paper will address the technical issues involved with high current, electron pulse operation and the near-term improvements to the electron optics, which will greatly improve the signal and spatial resolutions, and to the laser system, which will allow tailored specimen and photocathode drive conditions
Energy Technology Data Exchange (ETDEWEB)
LaGrange, Thomas [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States)], E-mail: lagrange@llnl.gov; Campbell, Geoffrey H.; Reed, B.W.; Taheri, Mitra; Pesavento, J. Bradley [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Kim, Judy S.; Browning, Nigel D. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Department of Chemical Engineering and Materials Science, University of California, One Shields Avenue, Davis, CA 95616 (United States)
2008-10-15
Most biological processes, chemical reactions and materials dynamics occur at rates much faster than can be captured with standard video rate acquisition methods in transmission electron microscopes (TEM). Thus, there is a need to increase the temporal resolution in order to capture and understand salient features of these rapid materials processes. This paper details the development of a high-time resolution dynamic transmission electron microscope (DTEM) that captures dynamics in materials with nanosecond time resolution. The current DTEM performance, having a spatial resolution <10 nm for single-shot imaging using 15 ns electron pulses, will be discussed in the context of experimental investigations in solid state reactions of NiAl reactive multilayer films, the study of martensitic transformations in nanocrystalline Ti and the catalytic growth of Si nanowires. In addition, this paper will address the technical issues involved with high current, electron pulse operation and the near-term improvements to the electron optics, which will greatly improve the signal and spatial resolutions, and to the laser system, which will allow tailored specimen and photocathode drive conditions.
Transmission dynamics and economics of rabies control in dogs and humans in an African city.
Zinsstag, J; Dürr, S; Penny, M A; Mindekem, R; Roth, F; Menendez Gonzalez, S; Naissengar, S; Hattendorf, J
2009-09-01
Human rabies in developing countries can be prevented through interventions directed at dogs. Potential cost-savings for the public health sector of interventions aimed at animal-host reservoirs should be assessed. Available deterministic models of rabies transmission between dogs were extended to include dog-to-human rabies transmission. Model parameters were fitted to routine weekly rabid-dog and exposed-human cases reported in N'Djaména, the capital of Chad. The estimated transmission rates between dogs (beta(d)) were 0.0807 km2/(dogs x week) and between dogs and humans (beta(dh)) 0.0002 km2/(dogs x week). The effective reproductive ratio (R(e)) at the onset of our observations was estimated at 1.01, indicating low-level endemic stability of rabies transmission. Human rabies incidence depended critically on dog-related transmission parameters. We simulated the effects of mass dog vaccination and the culling of a percentage of the dog population on human rabies incidence. A single parenteral dog rabies-mass vaccination campaign achieving a coverage of least 70% appears to be sufficient to interrupt transmission of rabies to humans for at least 6 years. The cost-effectiveness of mass dog vaccination was compared to postexposure prophylaxis (PEP), which is the current practice in Chad. PEP does not reduce future human exposure. Its cost-effectiveness is estimated at US $46 per disability adjusted life-years averted. Cost-effectiveness for PEP, together with a dog-vaccination campaign, breaks even with cost-effectiveness of PEP alone after almost 5 years. Beyond a time-frame of 7 years, it appears to be more cost-effective to combine parenteral dog-vaccination campaigns with human PEP compared to human PEP alone.
Study on the dynamics responses of a transmission system made from carbon nanotubes
International Nuclear Information System (INIS)
Yin, Hang; Cai, Kun; Wei, Ning; Qin, Qing-Hua; Shi, Jiao
2015-01-01
A rotational transmission system from coaxial carbon nanotubes (CNTs) is investigated using a computational molecular dynamics approach. The system consists of a motor from a single-walled carbon nanotube and a bearing from a double-walled carbon nanotube. The motor has a high fixed rotational frequency and the two ends of the outer tube in the bearing are fixed. The inner tube in the bearing works as a rotor. Because of the interlayer friction in the bearing, configurations of the joint between the adjacent ends of motor and rotor have significant effects on rotational transmission properties. Four factors are considered in simulation, i.e., the bonding types of atoms (sp 1 and sp 2 ) on the ends of motor and rotor, the difference between motor and rotor radii, the rotational speed of motor, and the environmental temperature. It is found that the synchronous transmission happens if the sp 1 atoms on the jointed ends of motor and rotor are bonded each other and become new sp 2 atoms. Therefore, the lower difference between radii of motor and rotor, higher temperature of environment leads to synchronous rotational transmission easily. If the environmental temperature is too low (e.g., <150 K), the end of motor adjacent to rotor is easily under buckling and new sp 2 atoms appear, too. With capped CNTs or higher radii difference between rotor and motor at an appropriate temperature, a stable asynchronous rotation of rotor can be generated, and the rotor's frequency varying linearly with motor's frequency between 230 and 270 GHz. A multi-signal transmission device combined with oscillating and rotational motion is proposed for motor and stator shares a same size in radius
Study on the dynamics responses of a transmission system made from carbon nanotubes
Energy Technology Data Exchange (ETDEWEB)
Yin, Hang; Cai, Kun, E-mail: kuicansj@163.com; Wei, Ning [College of Water Resources and Architectural Engineering, Northwest A and F University, Yangling 712100 (China); Qin, Qing-Hua [Research School of Engineering, The Australian National University, Canberra, Australian Capital Territory 2601 (Australia); Shi, Jiao [Department of Civil and Environmental Engineering, University of Missouri, Columbia, Missouri 65211-2200 (United States)
2015-06-21
A rotational transmission system from coaxial carbon nanotubes (CNTs) is investigated using a computational molecular dynamics approach. The system consists of a motor from a single-walled carbon nanotube and a bearing from a double-walled carbon nanotube. The motor has a high fixed rotational frequency and the two ends of the outer tube in the bearing are fixed. The inner tube in the bearing works as a rotor. Because of the interlayer friction in the bearing, configurations of the joint between the adjacent ends of motor and rotor have significant effects on rotational transmission properties. Four factors are considered in simulation, i.e., the bonding types of atoms (sp{sup 1} and sp{sup 2}) on the ends of motor and rotor, the difference between motor and rotor radii, the rotational speed of motor, and the environmental temperature. It is found that the synchronous transmission happens if the sp{sup 1} atoms on the jointed ends of motor and rotor are bonded each other and become new sp{sup 2} atoms. Therefore, the lower difference between radii of motor and rotor, higher temperature of environment leads to synchronous rotational transmission easily. If the environmental temperature is too low (e.g., <150 K), the end of motor adjacent to rotor is easily under buckling and new sp{sup 2} atoms appear, too. With capped CNTs or higher radii difference between rotor and motor at an appropriate temperature, a stable asynchronous rotation of rotor can be generated, and the rotor's frequency varying linearly with motor's frequency between 230 and 270 GHz. A multi-signal transmission device combined with oscillating and rotational motion is proposed for motor and stator shares a same size in radius.
Energy Technology Data Exchange (ETDEWEB)
NONE
1994-02-24
The Natural Gas Transmission and Distribution Model (NGTDM) is a component of the National Energy Modeling System (NEMS) used to represent the domestic natural gas transmission and distribution system. NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the Energy Information Administration (EIA) and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. This report documents the archived version of NGTDM that was used to produce the natural gas forecasts used in support of the Annual Energy Outlook 1994, DOE/EIA-0383(94). The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic design, provides detail on the methodology employed, and describes the model inputs, outputs, and key assumptions. It is intended to fulfill the legal obligation of the EIA to provide adequate documentation in support of its models (Public Law 94-385, Section 57.b.2). This report represents Volume 1 of a two-volume set. (Volume 2 will report on model performance, detailing convergence criteria and properties, results of sensitivity testing, comparison of model outputs with the literature and/or other model results, and major unresolved issues.) Subsequent chapters of this report provide: (1) an overview of the NGTDM (Chapter 2); (2) a description of the interface between the National Energy Modeling System (NEMS) and the NGTDM (Chapter 3); (3) an overview of the solution methodology of the NGTDM (Chapter 4); (4) the solution methodology for the Annual Flow Module (Chapter 5); (5) the solution methodology for the Distributor Tariff Module (Chapter 6); (6) the solution methodology for the Capacity Expansion Module (Chapter 7); (7) the solution methodology for the Pipeline Tariff Module (Chapter 8); and (8) a description of model assumptions, inputs, and outputs (Chapter 9).
Dynamics of annular bright field imaging in scanning transmission electron microscopy
International Nuclear Information System (INIS)
Findlay, S.D.; Shibata, N.; Sawada, H.; Okunishi, E.; Kondo, Y.; Ikuhara, Y.
2010-01-01
We explore the dynamics of image formation in the so-called annular bright field mode in scanning transmission electron microscopy, whereby an annular detector is used with detector collection range lying within the cone of illumination, i.e. the bright field region. We show that this imaging mode allows us to reliably image both light and heavy columns over a range of thickness and defocus values, and we explain the contrast mechanisms involved. The role of probe and detector aperture sizes is considered, as is the sensitivity of the method to intercolumn spacing and local disorder.
Farjoud, Alireza; Taylor, Russell; Schumann, Eric; Schlangen, Timothy
2014-02-01
This paper is focused on modelling, design, and testing of semi-active magneto-rheological (MR) engine and transmission mounts used in the automotive industry. The purpose is to develop a complete analysis, synthesis, design, and tuning tool that reduces the need for expensive and time-consuming laboratory and field tests. A detailed mathematical model of such devices is developed using multi-physics modelling techniques for physical systems with various energy domains. The model includes all major features of an MR mount including fluid dynamics, fluid track, elastic components, decoupler, rate-dip, gas-charged chamber, MR fluid rheology, magnetic circuit, electronic driver, and control algorithm. Conventional passive hydraulic mounts can also be studied using the same mathematical model. The model is validated using standard experimental procedures. It is used for design and parametric study of mounts; effects of various geometric and material parameters on dynamic response of mounts can be studied. Additionally, this model can be used to test various control strategies to obtain best vibration isolation performance by tuning control parameters. Another benefit of this work is that nonlinear interactions between sub-components of the mount can be observed and investigated. This is not possible by using simplified linear models currently available.
Directory of Open Access Journals (Sweden)
Ulrich Muellner
2018-06-01
Full Text Available Mathematical models of disease transmission are used to improve our understanding of patterns of infection and to identify factors influencing them. During recent public and animal health crises, such as pandemic influenza, Ebola, Zika, foot-and-mouth disease, models have made important contributions in addressing policy questions, especially through the assessment of the trajectory and scale of outbreaks, and the evaluation of control interventions. However, their mathematical formulation means that they may appear as a “black box” to those without the appropriate mathematical background. This may lead to a negative perception of their utility for guiding policy, and generate expectations, which are not in line with what these models can deliver. It is therefore important for policymakers, as well as public health and animal health professionals and researchers who collaborate with modelers and use results generated by these models for policy development or research purpose, to understand the key concepts and assumptions underlying these models.The software application epidemix (http://shinyapps.rvc.ac.uk presented here aims to make mathematical models of disease transmission accessible to a wider audience of users. By developing a visual interface for a suite of eight models, users can develop an understanding of the impact of various modelling assumptions – especially mixing patterns – on the trajectory of an epidemic and the impact of control interventions, without having to directly deal with the complexity of mathematical equations and programming languages. Models are compartmental or individual-based, deterministic or stochastic, and assume homogeneous or heterogeneous-mixing patterns (with the probability of transmission depending on the underlying structure of contact networks, or the spatial distribution of hosts. This application is intended to be used by scientists teaching mathematical modelling short courses to non
Wang, Lei; Fan, Youping; Zhang, Dai; Ge, Mengxin; Zou, Xianbin; Li, Jingjiao
2017-09-01
This paper proposes a method to simulate a back-to-back modular multilevel converter (MMC) HVDC transmission system. In this paper we utilize an equivalent networks to simulate the dynamic power system. Moreover, to account for the performance of converter station, core components of model of the converter station gives a basic model of simulation. The proposed method is applied to an equivalent real power system.
Estimating PMTCT's Impact on Heterosexual HIV Transmission: A Mathematical Modeling Analysis.
Directory of Open Access Journals (Sweden)
Aditya S Khanna
Full Text Available Prevention of mother-to-child HIV transmission (PMTCT strategies include combined short-course antiretrovirals during pregnancy (Option A, triple-drug antiretroviral treament (ART during pregnancy and breastfeeding (Option B, or lifelong ART (Option B+. The WHO also recommends ART for HIV treatment and prevention of sexual transmission of HIV. The impact of PMTCT strategies on prevention of sexual HIV transmission of HIV is not known. We estimated the population-level impact of PMTCT interventions on heterosexual HIV transmission in southwestern Uganda and KwaZulu-Natal, South Africa, two regions with different HIV prevalence and fertility rates.We constructed and validated dynamic, stochastic, network-based HIV transmission models for each region. PMTCT Options A, B, and B+ were simulated over ten years under three scenarios: 1 current ART and PMTCT coverage, 2 current ART and high PMTCT coverage, and 3 high ART and PMTCT coverage. We compared adult HIV incidence after ten years of each intervention to Option A (and current ART at current coverage.At current coverage, Options B and B+ reduced heterosexual HIV incidence by about 5% and 15%, respectively, in both countries. With current ART and high PMTCT coverage, Option B+ reduced HIV incidence by 35% in Uganda and 19% in South Africa, while Option B had smaller, but meaningful, reductions. The greatest reductions in HIV incidence were achieved with high ART and PMTCT coverage. In this scenario, all PMTCT strategies yielded similar results.Implementation of Options B/B+ reduces adult HIV incidence, with greater effect (relative to Option A at current levels in Uganda than South Africa. These results are likely driven by Uganda's higher fertility rates.
Modelling H5N1 in Bangladesh across spatial scales: Model complexity and zoonotic transmission risk
Directory of Open Access Journals (Sweden)
Edward M. Hill
2017-09-01
Full Text Available Highly pathogenic avian influenza H5N1 remains a persistent public health threat, capable of causing infection in humans with a high mortality rate while simultaneously negatively impacting the livestock industry. A central question is to determine regions that are likely sources of newly emerging influenza strains with pandemic causing potential. A suitable candidate is Bangladesh, being one of the most densely populated countries in the world and having an intensifying farming system. It is therefore vital to establish the key factors, specific to Bangladesh, that enable both continued transmission within poultry and spillover across the human–animal interface. We apply a modelling framework to H5N1 epidemics in the Dhaka region of Bangladesh, occurring from 2007 onwards, that resulted in large outbreaks in the poultry sector and a limited number of confirmed human cases. This model consisted of separate poultry transmission and zoonotic transmission components. Utilising poultry farm spatial and population information a set of competing nested models of varying complexity were fitted to the observed case data, with parameter inference carried out using Bayesian methodology and goodness-of-fit verified by stochastic simulations. For the poultry transmission component, successfully identifying a model of minimal complexity, which enabled the accurate prediction of the size and spatial distribution of cases in H5N1 outbreaks, was found to be dependent on the administration level being analysed. A consistent outcome of non-optimal reporting of infected premises materialised in each poultry epidemic of interest, though across the outbreaks analysed there were substantial differences in the estimated transmission parameters. The zoonotic transmission component found the main contributor to spillover transmission of H5N1 in Bangladesh was found to differ from one poultry epidemic to another. We conclude by discussing possible explanations for
Dose-response relationships for environmentally mediated infectious disease transmission models.
Directory of Open Access Journals (Sweden)
Andrew F Brouwer
2017-04-01
Full Text Available Environmentally mediated infectious disease transmission models provide a mechanistic approach to examining environmental interventions for outbreaks, such as water treatment or surface decontamination. The shift from the classical SIR framework to one incorporating the environment requires codifying the relationship between exposure to environmental pathogens and infection, i.e. the dose-response relationship. Much of the work characterizing the functional forms of dose-response relationships has used statistical fit to experimental data. However, there has been little research examining the consequences of the choice of functional form in the context of transmission dynamics. To this end, we identify four properties of dose-response functions that should be considered when selecting a functional form: low-dose linearity, scalability, concavity, and whether it is a single-hit model. We find that i middle- and high-dose data do not constrain the low-dose response, and different dose-response forms that are equally plausible given the data can lead to significant differences in simulated outbreak dynamics; ii the choice of how to aggregate continuous exposure into discrete doses can impact the modeled force of infection; iii low-dose linear, concave functions allow the basic reproduction number to control global dynamics; and iv identifiability analysis offers a way to manage multiple sources of uncertainty and leverage environmental monitoring to make inference about infectivity. By applying an environmentally mediated infectious disease model to the 1993 Milwaukee Cryptosporidium outbreak, we demonstrate that environmental monitoring allows for inference regarding the infectivity of the pathogen and thus improves our ability to identify outbreak characteristics such as pathogen strain.
Multiscale modeling of pedestrian dynamics
Cristiani, Emiliano; Tosin, Andrea
2014-01-01
This book presents mathematical models and numerical simulations of crowd dynamics. The core topic is the development of a new multiscale paradigm, which bridges the microscopic and macroscopic scales taking the most from each of them for capturing the relevant clues of complexity of crowds. The background idea is indeed that most of the complex trends exhibited by crowds are due to an intrinsic interplay between individual and collective behaviors. The modeling approach promoted in this book pursues actively this intuition and profits from it for designing general mathematical structures susceptible of application also in fields different from the inspiring original one. The book considers also the two most traditional points of view: the microscopic one, in which pedestrians are tracked individually, and the macroscopic one, in which pedestrians are assimilated to a continuum. Selected existing models are critically analyzed. The work is addressed to researchers and graduate students.
Sakata, Ren; Tomioka, Tazuko; Kobayashi, Takahiro
When cognitive radio (CR) systems dynamically use the frequency band, a control signal is necessary to indicate which carrier frequencies are currently available in the network. In order to keep efficient spectrum utilization, this control signal also should be transmitted based on the channel conditions. If transmitters dynamically select carrier frequencies, receivers have to receive control signals without knowledge of their carrier frequencies. To enable such transmission and reception, this paper proposes a novel scheme called DCPT (Differential Code Parallel Transmission). With DCPT, receivers can receive low-rate information with no knowledge of the carrier frequencies. The transmitter transmits two signals whose carrier frequencies are spaced by a predefined value. The absolute values of the carrier frequencies can be varied. When the receiver acquires the DCPT signal, it multiplies the signal by a frequency-shifted version of the signal; this yields a DC component that represents the data signal which is then demodulated. The performance was evaluated by means of numerical analysis and computer simulation. We confirmed that DCPT operates successfully even under severe interference if its parameters are appropriately configured.
Directory of Open Access Journals (Sweden)
Henry de-Graft Acquah
2013-01-01
Full Text Available Information Criteria provides an attractive basis for selecting the best model from a set of competing asymmetric price transmission models or theories. However, little is understood about the sensitivity of the model selection methods to model complexity. This study therefore fits competing asymmetric price transmission models that differ in complexity to simulated data and evaluates the ability of the model selection methods to recover the true model. The results of Monte Carlo experimentation suggest that in general BIC, CAIC and DIC were superior to AIC when the true data generating process was the standard error correction model, whereas AIC was more successful when the true model was the complex error correction model. It is also shown that the model selection methods performed better in large samples for a complex asymmetric data generating process than with a standard asymmetric data generating process. Except for complex models, AIC's performance did not make substantial gains in recovery rates as sample size increased. The research findings demonstrate the influence of model complexity in asymmetric price transmission model comparison and selection.
Extracting key information from historical data to quantify the transmission dynamics of smallpox
Directory of Open Access Journals (Sweden)
Brockmann Stefan O
2008-08-01
Full Text Available Abstract Background Quantification of the transmission dynamics of smallpox is crucial for optimizing intervention strategies in the event of a bioterrorist attack. This article reviews basic methods and findings in mathematical and statistical studies of smallpox which estimate key transmission parameters from historical data. Main findings First, critically important aspects in extracting key information from historical data are briefly summarized. We mention different sources of heterogeneity and potential pitfalls in utilizing historical records. Second, we discuss how smallpox spreads in the absence of interventions and how the optimal timing of quarantine and isolation measures can be determined. Case studies demonstrate the following. (1 The upper confidence limit of the 99th percentile of the incubation period is 22.2 days, suggesting that quarantine should last 23 days. (2 The highest frequency (61.8% of secondary transmissions occurs 3–5 days after onset of fever so that infected individuals should be isolated before the appearance of rash. (3 The U-shaped age-specific case fatality implies a vulnerability of infants and elderly among non-immune individuals. Estimates of the transmission potential are subsequently reviewed, followed by an assessment of vaccination effects and of the expected effectiveness of interventions. Conclusion Current debates on bio-terrorism preparedness indicate that public health decision making must account for the complex interplay and balance between vaccination strategies and other public health measures (e.g. case isolation and contact tracing taking into account the frequency of adverse events to vaccination. In this review, we summarize what has already been clarified and point out needs to analyze previous smallpox outbreaks systematically.
Wu, Guang; Dong, Zuomin
2017-09-01
Hybrid electric vehicles are widely accepted as a promising short to mid-term technical solution due to noticeably improved efficiency and lower emissions at competitive costs. In recent years, various hybrid powertrain systems were proposed and implemented based on different types of conventional transmission. Power-split system, including Toyota Hybrid System and Ford Hybrid System, are well-known examples. However, their relatively low torque capacity, and the drive of alternative and more advanced designs encouraged other innovative hybrid system designs. In this work, a new type of hybrid powertrain system based hybridized automated manual transmission (HAMT) is proposed. By using the concept of torque gap filler (TGF), this new hybrid powertrain type has the potential to overcome issue of torque gap during gearshift. The HAMT design (patent pending) is described in details, from gear layout and design of gear ratios (EV mode and HEV mode) to torque paths at different gears. As an analytical tool, mutli-body model of vehicle equipped with this HAMT was built to analyze powertrain dynamics at various steady and transient modes. A gearshift was decomposed and analyzed based basic modes. Furthermore, a Simulink-SimDriveline hybrid vehicle model was built for the new transmission, driveline and vehicle modular. Control strategy has also been built to harmonically coordinate different powertrain components to realize TGF function. A vehicle launch simulation test has been completed under 30% of accelerator pedal position to reveal details during gearshift. Simulation results showed that this HAMT can eliminate most torque gap that has been persistent issue of traditional AMT, improving both drivability and performance. This work demonstrated a new type of transmission that features high torque capacity, high efficiency and improved drivability.
Modeling infection transmission in primate networks to predict centrality-based risk.
Romano, Valéria; Duboscq, Julie; Sarabian, Cécile; Thomas, Elodie; Sueur, Cédric; MacIntosh, Andrew J J
2016-07-01
Social structure can theoretically regulate disease risk by mediating exposure to pathogens via social proximity and contact. Investigating the role of central individuals within a network may help predict infectious agent transmission as well as implement disease control strategies, but little is known about such dynamics in real primate networks. We combined social network analysis and a modeling approach to better understand transmission of a theoretical infectious agent in wild Japanese macaques, highly social animals which form extended but highly differentiated social networks. We collected focal data from adult females living on the islands of Koshima and Yakushima, Japan. Individual identities as well as grooming networks were included in a Markov graph-based simulation. In this model, the probability that an individual will transmit an infectious agent depends on the strength of its relationships with other group members. Similarly, its probability of being infected depends on its relationships with already infected group members. We correlated: (i) the percentage of subjects infected during a latency-constrained epidemic; (ii) the mean latency to complete transmission; (iii) the probability that an individual is infected first among all group members; and (iv) each individual's mean rank in the chain of transmission with different individual network centralities (eigenvector, strength, betweenness). Our results support the hypothesis that more central individuals transmit infections in a shorter amount of time and to more subjects but also become infected more quickly than less central individuals. However, we also observed that the spread of infectious agents on the Yakushima network did not always differ from expectations of spread on random networks. Generalizations about the importance of observed social networks in pathogen flow should thus be made with caution, since individual characteristics in some real world networks appear less relevant than
Modelling the geographic distribution of wind power and the impact on transmission needs
DEFF Research Database (Denmark)
Østergaard, Poul Alberg
2003-01-01
Through energy systems modelling, transmission systems modelling and geographical modelling, the article examines the sensitivity of the response of the transmission system to the geographic distributions of wind power and in particular the sensitivity of the results to the accuracy...... of the distributed modelled. The results show that accuracy of the geographic modelling while important for the analysis of specific single transmission lines is not important for the analysis of the general response of the transmission system. The analyses thus corroborate previous analyses that demonstrated...
Aggregated Wind Park Models for Analysing Power System Dynamics
Energy Technology Data Exchange (ETDEWEB)
Poeller, Markus; Achilles, Sebastian [DIgSILENT GmbH, Gomaringen (Germany)
2003-11-01
The increasing amount of wind power generation in European power systems requires stability analysis considering interaction between wind-farms and transmission systems. Dynamics introduced by dispersed wind generators at the distribution level can usually be neglected. However, large on- and offshore wind farms have a considerable influence to power system dynamics and must definitely be considered for analyzing power system dynamics. Compared to conventional power stations, wind power plants consist of a large number of generators of small size. Therefore, representing every wind generator individually increases the calculation time of dynamic simulations considerably. Therefore, model aggregation techniques should be applied for reducing calculation times. This paper presents aggregated models for wind parks consisting of fixed or variable speed wind generators.
International Nuclear Information System (INIS)
Rathke, Christian
2013-01-01
The liberalisation of electricity markets and the increase of renewable energy generation actually causes dramatic changes for the whole European power industry. The transmission system operators in particular have to meet the challenge to ensure a stable and reliable system operation in the future. Significant changes in power generation will require a substantial extension to current inadequate original transmission grids to handle increased wide area power flows. This is the only way to avoid overloading the grid and to reduce the herefrom resulting limitations for the Pan-European cross-border trade of electricity. This work describes in detail the development of a Pan-European integrated grid and an electricity market simulation tool. For this purpose an overview about the today's structure of the European electricity industry is given initially. Afterwards the configuration of the transmission grid, the used equipment and different methods for the load flow and short circuit calculation are explained. Furthermore models for the calculation of local loads and the power plant dispatch are presented in the following chapters. Following on from this a detailed model of the European electricity industry is developed and the main functions are described by means of some exemplary simulations. The simulation tool developed in this work enables the user to calculate realistic power plant schedules and the consequent resulting physical effects on the European transmission grid. It combines a time series based simulation of the electricity market with a detailed model of the transmission grid. The highly detailing of the model offers the feasibility to execute a complete AC load flow calculation using the Newton Raphson algorithm.Therefore it is possible to identify the active as well as the reactive power flows in the grid. The results of the power flow calculation are the basis for further investigations (e. g. the short circuit calculation) and to decide on
Characterizing and Modeling Citation Dynamics
Eom, Young-Ho; Fortunato, Santo
2011-01-01
Citation distributions are crucial for the analysis and modeling of the activity of scientists. We investigated bibliometric data of papers published in journals of the American Physical Society, searching for the type of function which best describes the observed citation distributions. We used the goodness of fit with Kolmogorov-Smirnov statistics for three classes of functions: log-normal, simple power law and shifted power law. The shifted power law turns out to be the most reliable hypothesis for all citation networks we derived, which correspond to different time spans. We find that citation dynamics is characterized by bursts, usually occurring within a few years since publication of a paper, and the burst size spans several orders of magnitude. We also investigated the microscopic mechanisms for the evolution of citation networks, by proposing a linear preferential attachment with time dependent initial attractiveness. The model successfully reproduces the empirical citation distributions and accounts for the presence of citation bursts as well. PMID:21966387
MATHEMATICAL MODEL FOR RIVERBOAT DYNAMICS
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Aleksander Grm
2017-01-01
Full Text Available Present work describes a simple dynamical model for riverboat motion based on the square drag law. Air and water interactions with the boat are determined from aerodynamic coefficients. CFX simulations were performed with fully developed turbulent flow to determine boat aerodynamic coefficients for an arbitrary angle of attack for the air and water portions separately. The effect of wave resistance is negligible compared to other forces. Boat movement analysis considers only two-dimensional motion, therefore only six aerodynamics coefficients are required. The proposed model is solved and used to determine the critical environmental parameters (wind and current under which river navigation can be conducted safely. Boat simulator was tested in a single area on the Ljubljanica river and estimated critical wind velocity.
Energy Technology Data Exchange (ETDEWEB)
Cipiti, Benjamin B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-03-01
The Co-Decontamination (CoDCon) Demonstration project is designed to test the separation of a mixed U and Pu product from dissolved spent nuclear fuel. The primary purpose of the project is to quantify the accuracy and precision to which a U/Pu mass ratio can be achieved without removing a pure Pu product. The system includes an on-line monitoring system using spectroscopy to monitor the ratios throughout the process. A dynamic model of the CoDCon flowsheet and on-line monitoring system was developed in order to expand the range of scenarios that can be examined for process control and determine overall measurement uncertainty. The model development and initial results are presented here.
Modeling the dynamics of choice.
Baum, William M; Davison, Michael
2009-06-01
A simple linear-operator model both describes and predicts the dynamics of choice that may underlie the matching relation. We measured inter-food choice within components of a schedule that presented seven different pairs of concurrent variable-interval schedules for 12 food deliveries each with no signals indicating which pair was in force. This measure of local choice was accurately described and predicted as obtained reinforcer sequences shifted it to favor one alternative or the other. The effect of a changeover delay was reflected in one parameter, the asymptote, whereas the effect of a difference in overall rate of food delivery was reflected in the other parameter, rate of approach to the asymptote. The model takes choice as a primary dependent variable, not derived by comparison between alternatives-an approach that agrees with the molar view of behaviour.
Directory of Open Access Journals (Sweden)
Smith Thomas A
2008-01-01
-heterogeneity predict lower incidence of infection at a given average exposure than do those assuming exposure to be uniform. The negative binomial model moreover provides an estimate of the variance of the within-cohort distribution of the EIR and hence of within cohort heterogeneity in exposure. Conclusion Apparent deviations from mass action kinetics in parasite transmission can arise from spatial and temporal heterogeneity in the inoculation rate, and from imprecision in its measurement. For parasites like P. falciparum, where there is no plausible biological rationale for deviations from mass action, this provides a strategy for estimating true levels of heterogeneity, since if mass-action is assumed, the within-population variance in exposure becomes identifiable in cohort studies relating infection to transmission intensity. Statistical analyses relating infection to exposure thus provide a valid general approach for estimating heterogeneity in transmission but only when they incorporate mass action kinetics and shrinkage estimates of exposure. Such analyses make it possible to include realistic levels of heterogeneity in dynamic models that predict the impact of control measures on transmission intensity.
Dynamical modeling of tidal streams
International Nuclear Information System (INIS)
Bovy, Jo
2014-01-01
I present a new framework for modeling the dynamics of tidal streams. The framework consists of simple models for the initial action-angle distribution of tidal debris, which can be straightforwardly evolved forward in time. Taking advantage of the essentially one-dimensional nature of tidal streams, the transformation to position-velocity coordinates can be linearized and interpolated near a small number of points along the stream, thus allowing for efficient computations of a stream's properties in observable quantities. I illustrate how to calculate the stream's average location (its 'track') in different coordinate systems, how to quickly estimate the dispersion around its track, and how to draw mock stream data. As a generative model, this framework allows one to compute the full probability distribution function and marginalize over or condition it on certain phase-space dimensions as well as convolve it with observational uncertainties. This will be instrumental in proper data analysis of stream data. In addition to providing a computationally efficient practical tool for modeling the dynamics of tidal streams, the action-angle nature of the framework helps elucidate how the observed width of the stream relates to the velocity dispersion or mass of the progenitor, and how the progenitors of 'orphan' streams could be located. The practical usefulness of the proposed framework crucially depends on the ability to calculate action-angle variables for any orbit in any gravitational potential. A novel method for calculating actions, frequencies, and angles in any static potential using a single orbit integration is described in the Appendix.
Model-based dynamic control and optimization of gas networks
Energy Technology Data Exchange (ETDEWEB)
Hofsten, Kai
2001-07-01
This work contributes to the research on control, optimization and simulation of gas transmission systems to support the dispatch personnel at gas control centres for the decision makings in the daily operation of the natural gas transportation systems. Different control and optimization strategies have been studied. The focus is on the operation of long distance natural gas transportation systems. Stationary optimization in conjunction with linear model predictive control using state space models is proposed for supply security, the control of quality parameters and minimization of transportation costs for networks offering transportation services. The result from the stationary optimization together with a reformulation of a simplified fluid flow model formulates a linear dynamic optimization model. This model is used in a finite time control and state constrained linear model predictive controller. The deviation from the control and the state reference determined from the stationary optimization is penalized quadratically. Because of the time varying status of infrastructure, the control space is also generally time varying. When the average load is expected to change considerably, a new stationary optimization is performed, giving a new state and control reference together with a new dynamic model that is used for both optimization and state estimation. Another proposed control strategy is a control and output constrained nonlinear model predictive controller for the operation of gas transmission systems. Here, the objective is also the security of the supply, quality control and minimization of transportation costs. An output vector is defined, which together with a control vector are both penalized quadratically from their respective references in the objective function. The nonlinear model predictive controller can be combined with a stationary optimization. At each sampling instant, a non convex nonlinear programming problem is solved giving a local minimum
Zhao, Bolin; Lv, Chen; Hofman, Theo; Steinbuch, Maarten; Zhang, Junzhi; Cao, Dongpu
2018-01-01
In this paper, gear ratios of a two-speed transmission system are optimized for an electric passenger car. Quasi static system models, including the vehicle model, the motor, the battery, the transmission system, and drive cycles are established in MATLAB/Simulink at first. Specifically, since the
A Bayesian framework for parameter estimation in dynamical models.
Directory of Open Access Journals (Sweden)
Flávio Codeço Coelho
Full Text Available Mathematical models in biology are powerful tools for the study and exploration of complex dynamics. Nevertheless, bringing theoretical results to an agreement with experimental observations involves acknowledging a great deal of uncertainty intrinsic to our theoretical representation of a real system. Proper handling of such uncertainties is key to the successful usage of models to predict experimental or field observations. This problem has been addressed over the years by many tools for model calibration and parameter estimation. In this article we present a general framework for uncertainty analysis and parameter estimation that is designed to handle uncertainties associated with the modeling of dynamic biological systems while remaining agnostic as to the type of model used. We apply the framework to fit an SIR-like influenza transmission model to 7 years of incidence data in three European countries: Belgium, the Netherlands and Portugal.
OISI dynamic end-to-end modeling tool
Kersten, Michael; Weidler, Alexander; Wilhelm, Rainer; Johann, Ulrich A.; Szerdahelyi, Laszlo
2000-07-01
The OISI Dynamic end-to-end modeling tool is tailored to end-to-end modeling and dynamic simulation of Earth- and space-based actively controlled optical instruments such as e.g. optical stellar interferometers. `End-to-end modeling' is meant to denote the feature that the overall model comprises besides optical sub-models also structural, sensor, actuator, controller and disturbance sub-models influencing the optical transmission, so that the system- level instrument performance due to disturbances and active optics can be simulated. This tool has been developed to support performance analysis and prediction as well as control loop design and fine-tuning for OISI, Germany's preparatory program for optical/infrared spaceborne interferometry initiated in 1994 by Dornier Satellitensysteme GmbH in Friedrichshafen.
A Mathematical Model of Malaria Transmission with Structured Vector Population and Seasonality
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Bakary Traoré
2017-01-01
Full Text Available In this paper, we formulate a mathematical model of nonautonomous ordinary differential equations describing the dynamics of malaria transmission with age structure for the vector population. The biting rate of mosquitoes is considered as a positive periodic function which depends on climatic factors. The basic reproduction ratio of the model is obtained and we show that it is the threshold parameter between the extinction and the persistence of the disease. Thus, by applying the theorem of comparison and the theory of uniform persistence, we prove that if the basic reproduction ratio is less than 1, then the disease-free equilibrium is globally asymptotically stable and if it is greater than 1, then there exists at least one positive periodic solution. Finally, numerical simulations are carried out to illustrate our analytical results.
Merkle, Jerod A.; Cross, Paul C.; Scurlock, Brandon M.; Cole, Eric K.; Courtemanch, Alyson B.; Dewey, Sarah R.; Kauffman, Matthew J.
2018-01-01
Disease models typically focus on temporal dynamics of infection, while often neglecting environmental processes that determine host movement. In many systems, however, temporal disease dynamics may be slow compared to the scale at which environmental conditions alter host space-use and accelerate disease transmission.Using a mechanistic movement modelling approach, we made space-use predictions of a mobile host (elk [Cervus Canadensis] carrying the bacterial disease brucellosis) under environmental conditions that change daily and annually (e.g., plant phenology, snow depth), and we used these predictions to infer how spring phenology influences the risk of brucellosis transmission from elk (through aborted foetuses) to livestock in the Greater Yellowstone Ecosystem.Using data from 288 female elk monitored with GPS collars, we fit step selection functions (SSFs) during the spring abortion season and then implemented a master equation approach to translate SSFs into predictions of daily elk distribution for five plausible winter weather scenarios (from a heavy snow, to an extreme winter drought year). We predicted abortion events by combining elk distributions with empirical estimates of daily abortion rates, spatially varying elk seroprevelance and elk population counts.Our results reveal strong spatial variation in disease transmission risk at daily and annual scales that is strongly governed by variation in host movement in response to spring phenology. For example, in comparison with an average snow year, years with early snowmelt are predicted to have 64% of the abortions occurring on feedgrounds shift to occurring on mainly public lands, and to a lesser extent on private lands.Synthesis and applications. Linking mechanistic models of host movement with disease dynamics leads to a novel bridge between movement and disease ecology. Our analysis framework offers new avenues for predicting disease spread, while providing managers tools to proactively mitigate
Viscoelastic dynamic models of resilient elements used in railway tracks
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Zbiciak Artur
2016-01-01
Full Text Available The paper presents selected theoretical aspects concerning viscoelastic dynamic modelling of resilient elements used in railway tracks. In order to characterize the research methodology for resilient mats in railway tracks, German Standards [1-4] are used herein. The main goal of the paper is to demonstrate the procedure of insertion loss calculation for a single degree of freedom truck system containing under-ballast mats. Selected results of certain dynamic characteristics of resilient truck systems (transmissibility, Bode and Nyquist plots etc. are also discussed. The results of calculations visualized in graphs, were obtained by using own applications written in programming language MATLAB.
Directory of Open Access Journals (Sweden)
R. Fargère
2012-01-01
Full Text Available Some interactions between the dynamic and tribological behaviour of geared transmissions are examined, and a number of experimental and simulation results are compared. A model is introduced which incorporates most of the possible interactions between gears, shafts and hydrodynamic journal bearings. It combines (i a specific element for wide-faced gears that includes the normal contact conditions between actual mating teeth, that is, with tooth shape deviations and mounting errors, (ii shaft finite elements, and (iii the external forces generated by journal bearings determined by directly solving Reynolds' equation. The simulation results are compared with the measurement obtained on a high-precision test rig with single-stage spur and helical gears supported by hydrodynamic journal bearings. The experimental and simulation results compare well thus validating the simulation strategy both at the global and local scales.
Studies on the population dynamics of a rumor-spreading model in online social networks
Dong, Suyalatu; Fan, Feng-Hua; Huang, Yong-Chang
2018-02-01
This paper sets up a rumor spreading model in online social networks based on the European fox rabies SIR model. The model considers the impact of changing number of online social network users, combines the transmission dynamics to set up a population dynamics of rumor spreading model in online social networks. Simulation is carried out on online social network, and results show that the new rumor spreading model is in accordance with the real propagation characteristics in online social networks.
Leelahapongsathon, Kansuda; Schukken, Ynte Hein; Pinyopummintr, Tanu; Suriyasathaporn, Witaya
2016-02-01
parameter and R0 values were not different between both pathogens; however, the duration of infection for Strep. agalactiae was longer than Strep. uberis. These suggest that Strep. uberis may have a different transmission dynamic compared with Strep. agalactiae. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
Xiao, Yanyu; Beier, John C.; Cantrell, Robert Stephen; Cosner, Chris; DeAngelis, Donald L.; Ruan, Shigui
2015-01-01
Rift Valley fever (RVF) is an important mosquito-borne viral zoonosis in Africa and the Middle East that causes human deaths and significant economic losses due to huge incidences of death and abortion among infected livestock. Outbreaks of RVF are sporadic and associated with both seasonal and socioeconomic effects. Here we propose an almost periodic three-patch model to investigate the transmission dynamics of RVF virus (RVFV) among ruminants with spatial movements. Our findings indicate that, in Northeastern Africa, human activities, including those associated with the Eid al Adha feast, along with a combination of climatic factors such as rainfall level and hydrological variations, contribute to the transmission and dispersal of the disease pathogen. Moreover, sporadic outbreaks may occur when the two events occur together: 1) abundant livestock are recruited into areas at risk from RVF due to the demand for the religious festival and 2) abundant numbers of mosquitoes emerge. These two factors have been shown to have impacts on the severity of RVF outbreaks. Our numerical results present the transmission dynamics of the disease pathogen over both short and long periods of time, particularly during the festival time. Further, we investigate the impact on patterns of disease outbreaks in each patch brought by festival- and seasonal-driven factors, such as the number of livestock imported daily, the animal transportation speed from patch to patch, and the death rate induced by ceremonial sacrifices. In addition, our simulations show that when the time for festival preparation starts earlier than usual, the risk of massive disease outbreaks rises, particularly in patch 3 (the place where the religious ceremony will be held).
Directory of Open Access Journals (Sweden)
Xianhong Li
2013-01-01
Full Text Available A general nonlinear time-varying (NLTV dynamic model and linear time-varying (LTV dynamic model are presented for shield tunnel boring machine (TBM cutterhead driving system, respectively. Different gear backlashes and mesh damped and transmission errors are considered in the NLTV dynamic model. The corresponding multiple-input and multiple-output (MIMO state space models are also presented. Through analyzing the linear dynamic model, the optimal reducer ratio (ORR and optimal transmission ratio (OTR are obtained for the shield TBM cutterhead driving system, respectively. The NLTV and LTV dynamic models are numerically simulated, and the effects of physical parameters under various conditions of NLTV dynamic model are analyzed. Physical parameters such as the load torque, gear backlash and transmission error, gear mesh stiffness and damped, pinions inertia and damped, large gear inertia and damped, and motor rotor inertia and damped are investigated in detail to analyze their effects on dynamic response and performances of the shield TBM cutterhead driving system. Some preliminary approaches are proposed to improve dynamic performances of the cutterhead driving system, and dynamic models will provide a foundation for shield TBM cutterhead driving system's cutterhead fault diagnosis, motion control, and torque synchronous control.
Directory of Open Access Journals (Sweden)
Siddhivinayak Hirve
2016-08-01
Full Text Available As Bangladesh, India and Nepal progress towards visceral leishmaniasis (VL elimination, it is important to understand the role of asymptomatic Leishmania infection (ALI, VL treatment relapse and post kala-azar dermal leishmaniasis (PKDL in transmission.We reviewed evidence systematically on ALI, relapse and PKDL. We searched multiple databases to include studies on burden, risk factors, biomarkers, natural history, and infectiveness of ALI, PKDL and relapse. After screening 292 papers, 98 were included covering the years 1942 through 2016. ALI, PKDL and relapse studies lacked a reference standard and appropriate biomarker. The prevalence of ALI was 4-17-fold that of VL. The risk of ALI was higher in VL case contacts. Most infections remained asymptomatic or resolved spontaneously. The proportion of ALI that progressed to VL disease within a year was 1.5-23%, and was higher amongst those with high antibody titres. The natural history of PKDL showed variability; 3.8-28.6% had no past history of VL treatment. The infectiveness of PKDL was 32-53%. The risk of VL relapse was higher with HIV co-infection. Modelling studies predicted a range of scenarios. One model predicted VL elimination was unlikely in the long term with early diagnosis. Another model estimated that ALI contributed to 82% of the overall transmission, VL to 10% and PKDL to 8%. Another model predicted that VL cases were the main driver for transmission. Different models predicted VL elimination if the sandfly density was reduced by 67% by killing the sandfly or by 79% by reducing their breeding sites, or with 4-6y of optimal IRS or 10y of sub-optimal IRS and only in low endemic setting.There is a need for xenodiagnostic and longitudinal studies to understand the potential of ALI and PKDL as reservoirs of infection.
System Dynamics Modelling for a Balanced Scorecard
DEFF Research Database (Denmark)
Nielsen, Steen; Nielsen, Erland Hejn
2008-01-01
/methodology/approach - We use a case study model to develop time or dynamic dimensions by using a System Dynamics modelling (SDM) approach. The model includes five perspectives and a number of financial and non-financial measures. All indicators are defined and related to a coherent number of different cause...... have a major influence on other indicators and profit and may be impossible to predict without using a dynamic model. Practical implications - The model may be used as the first step in quantifying the cause-and-effect relationships of an integrated BSC model. Using the System Dynamics model provides......Purpose - To construct a dynamic model/framework inspired by a case study based on an international company. As described by the theory, one of the main difficulties of BSC is to foresee the time lag dimension of different types of indicators and their combined dynamic effects. Design...
An individual-based model of transmission of resistant bacteria in a veterinary teaching hospital.
Directory of Open Access Journals (Sweden)
Neeraj Suthar
Full Text Available Veterinary nosocomial infections caused by antibiotic resistant bacteria cause increased morbidity, higher cost and length of treatment and increased zoonotic risk because of the difficulty in treating them. In this study, an individual-based model was developed to investigate the effects of movements of canine patients among ten areas (transmission points within a veterinary teaching hospital, and the effects of these movements on transmission of antibiotic susceptible and resistant pathogens. The model simulates contamination of transmission points, healthcare workers, and patients as well as the effects of decontamination of transmission points, disinfection of healthcare workers, and antibiotic treatments of canine patients. The model was parameterized using data obtained from hospital records, information obtained by interviews with hospital staff, and the published literature. The model suggested that transmission resulting from contact with healthcare workers was common, and that certain transmission points (housing wards, diagnostics room, and the intensive care unit presented higher risk for transmission than others (lobby and surgery. Sensitivity analyses using a range of parameter values demonstrated that the risk of acquisition of colonization by resistant pathogens decreased with shorter patient hospital stays (P<0.0001, more frequent decontamination of transmission points and disinfection of healthcare workers (P<0.0001 and better compliance of healthcare workers with hygiene practices (P<0.0001. More frequent decontamination of heavily trafficked transmission points was especially effective at reducing transmission of the model pathogen.
Natural Gas Transmission and Distribution Model of the National Energy Modeling System. Volume 1
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-01-01
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. The NGTDM is the model within the NEMS that represents the transmission, distribution, and pricing of natural gas. The model also includes representations of the end-use demand for natural gas, the production of domestic natural gas, and the availability of natural gas traded on the international market based on information received from other NEMS models. The NGTDM determines the flow of natural gas in an aggregate, domestic pipeline network, connecting domestic and foreign supply regions with 12 demand regions. The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic design, provides detail on the methodology employed, and describes the model inputs, outputs, and key assumptions. Subsequent chapters of this report provide: an overview of NGTDM; a description of the interface between the NEMS and NGTDM; an overview of the solution methodology of the NGTDM; the solution methodology for the Annual Flow Module; the solution methodology for the Distributor Tariff Module; the solution methodology for the Capacity Expansion Module; the solution methodology for the Pipeline Tariff Module; and a description of model assumptions, inputs, and outputs.
ELABORATION OF THE COMPUTATIONAL MODEL OF THE PLANETARY PRECESSIONAL TRANSMISSION
Directory of Open Access Journals (Sweden)
BOSTAN Ion
2010-07-01
Full Text Available The specific character of sphere-spatial motion used in the precessional transmissions makes impossible the utilization of involute profiles of classical teeth. This fact requires the elaboration of new non-standard profiles, which in conditions of using the sphere-spatial motion with an immovable point of the satellite would assure constancy transfer function, the multiplicity of the precessional gear and consequently high carrying capacity of the precessional transmission in general.
Medium-term electric power demand forecasting based on economic-electricity transmission model
Li, Wenfeng; Bao, Fangmin; Bai, Hongkun; Liu, Wei; Liu, Yongmin; Mao, Yubin; Wang, Jiangbo; Liu, Junhui
2018-06-01
Electric demand forecasting is a basic work to ensure the safe operation of power system. Based on the theories of experimental economics and econometrics, this paper introduces Prognoz Platform 7.2 intelligent adaptive modeling platform, and constructs the economic electricity transmission model that considers the economic development scenarios and the dynamic adjustment of industrial structure to predict the region's annual electricity demand, and the accurate prediction of the whole society's electricity consumption is realized. Firstly, based on the theories of experimental economics and econometrics, this dissertation attempts to find the economic indicator variables that drive the most economical growth of electricity consumption and availability, and build an annual regional macroeconomic forecast model that takes into account the dynamic adjustment of industrial structure. Secondly, it innovatively put forward the economic electricity directed conduction theory and constructed the economic power transfer function to realize the group forecast of the primary industry + rural residents living electricity consumption, urban residents living electricity, the second industry electricity consumption, the tertiary industry electricity consumption; By comparing with the actual value of economy and electricity in Henan province in 2016, the validity of EETM model is proved, and the electricity consumption of the whole province from 2017 to 2018 is predicted finally.
Dynamics of soft Nanomaterials captured by transmission electron microscopy in liquid water
Energy Technology Data Exchange (ETDEWEB)
Proetto, Maria T.; Rush, Anthony M.; Chien, Miao-Ping; Abellan Baeza, Patricia; Patterson, Joseph P.; Thompson, Matthew P.; Olson, Norman H.; Moore, Curtis E.; Rheingold, Arnold L.; Andolina, Christopher; Millstone, Jill; Howell, Stephen B.; Browning, Nigel D.; Evans, James E.; Gianneschi, Nathan C.
2014-01-14
In this paper we present in situ transmission electron microscopy (TEM) of soft, synthetic nanoparticles with a comparative analysis using conventional TEM methods. This comparison is made with the simple aim of describing what is an unprecedented example of in situ imaging by TEM. However, we contend the technique will quickly become essential in the characterization of analogous systems, especially where dynamics are of interest in the solvated state. In this case, particles were studied which were obtained from the direct polymerization of an oxaliplatin analog, designed for an ongoing program in novel chemotherapeutic delivery systems. The resulting nanoparticles provided sufficient contrast for facile imaging in situ, and point toward key design parameters that enable this new characterization approach for organic nanomaterials. We describe the preparation of the synthetic micellar nanoparticles to- gether with their characterization in liquid water.
Transmission Loss Calculation using A and B Loss Coefficients in Dynamic Economic Dispatch Problem
Jethmalani, C. H. Ram; Dumpa, Poornima; Simon, Sishaj P.; Sundareswaran, K.
2016-04-01
This paper analyzes the performance of A-loss coefficients while evaluating transmission losses in a Dynamic Economic Dispatch (DED) Problem. The performance analysis is carried out by comparing the losses computed using nominal A loss coefficients and nominal B loss coefficients in reference with load flow solution obtained by standard Newton-Raphson (NR) method. Density based clustering method based on connected regions with sufficiently high density (DBSCAN) is employed in identifying the best regions of A and B loss coefficients. Based on the results obtained through cluster analysis, a novel approach in improving the accuracy of network loss calculation is proposed. Here, based on the change in per unit load values between the load intervals, loss coefficients are updated for calculating the transmission losses. The proposed algorithm is tested and validated on IEEE 6 bus system, IEEE 14 bus, system IEEE 30 bus system and IEEE 118 bus system. All simulations are carried out using SCILAB 5.4 (www.scilab.org) which is an open source software.
Keiser, Carl N; Pinter-Wollman, Noa; Ziemba, Michael J; Kothamasu, Krishna S; Pruitt, Jonathan N
2018-03-01
The traits of the primary case of an infectious disease outbreak, and the circumstances for their aetiology, potentially influence the trajectory of transmission dynamics. However, these dynamics likely also depend on the traits of the individuals with whom the primary case interacts. We used the social spider Stegodyphus dumicola to test how the traits of the primary case, group phenotypic composition and group size interact to facilitate the transmission of a GFP-labelled cuticular bacterium. We also compared bacterial transmission across experimentally generated "daisy-chain" vs. "star" networks of social interactions. Finally, we compared social network structure across groups of different sizes. Groups of 10 spiders experienced more bacterial transmission events compared to groups of 30 spiders, regardless of groups' behavioural composition. Groups containing only one bold spider experienced the lowest levels of bacterial transmission regardless of group size. We found no evidence for the traits of the primary case influencing any transmission dynamics. In a second experiment, bacteria were transmitted to more individuals in experimentally induced star networks than in daisy-chains, on which transmission never exceeded three steps. In both experimental network types, transmission success depended jointly on the behavioural traits of the interacting individuals; however, the behavioural traits of the primary case were only important for transmission on star networks. Larger social groups exhibited lower interaction density (i.e. had a low ratio of observed to possible connections) and were more modular, i.e. they had more connections between nodes within a subgroup and fewer connections across subgroups. Thus, larger groups may restrict transmission by forming fewer interactions and by isolating subgroups that interacted with the primary case. These findings suggest that accounting for the traits of single exposed hosts has less power in predicting transmission
Barlow, John W; Zadoks, Ruth N; Schukken, Ynte H
2013-02-11
Treatment of subclinical mastitis during lactation can have both direct (individual animal level) and indirect (population level) effects. With a few exceptions, prior research has focused on evaluating the direct effects of mastitis treatment, and to date no controlled field trials have been conducted to test whether beneficial indirect effects of lactation treatment strategies targeting subclinical mastitis can be demonstrated on commercial dairy farms. Furthermore, there is limited knowledge on the impact of such interventions on the population dynamics of specific bacterial strains. The purpose of this study was to test the hypothesis that lactation therapy targeting S. aureus subclinical intramammary infection reduces transmission of S. aureus strains within dairy herds. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to determine strain specific infection dynamics in treated and control groups in a split herd trial conducted on 2 commercial dairy farms. The direct effect of 8 days intramammary lactation therapy with pirlimycin hydrochloride was demonstrated by an increased proportion of cure and a reduction in duration of infection in quarters receiving treatment compared to untreated controls. The indirect effect of lactation therapy was demonstrated by reduction of new S. aureus intramammary infections (IMI) caused by the dominant strain type in both herds. Strain typing of representative isolates taken over the duration of all IMI, including pre- and post-treatment isolates, provided more precise estimates of new infection, cure, and re-infection rates. New S. aureus infections in recovered susceptible quarters and the emergence of a new strain type in one herd influenced incidence measures. In addition to demonstrating positive direct effects of lactation therapy, this study provides evidence that treatment of subclinical S. aureus mastitis during lactation can have indirect effects including preventing new IMI and
Directory of Open Access Journals (Sweden)
Barlow John W
2013-02-01
Full Text Available Abstract Background Treatment of subclinical mastitis during lactation can have both direct (individual animal level and indirect (population level effects. With a few exceptions, prior research has focused on evaluating the direct effects of mastitis treatment, and to date no controlled field trials have been conducted to test whether beneficial indirect effects of lactation treatment strategies targeting subclinical mastitis can be demonstrated on commercial dairy farms. Furthermore, there is limited knowledge on the impact of such interventions on the population dynamics of specific bacterial strains. The purpose of this study was to test the hypothesis that lactation therapy targeting S. aureus subclinical intramammary infection reduces transmission of S. aureus strains within dairy herds. Pulsed-field gel electrophoresis (PFGE and multilocus sequence typing (MLST were used to determine strain specific infection dynamics in treated and control groups in a split herd trial conducted on 2 commercial dairy farms. Results The direct effect of 8 days intramammary lactation therapy with pirlimycin hydrochloride was demonstrated by an increased proportion of cure and a reduction in duration of infection in quarters receiving treatment compared to untreated controls. The indirect effect of lactation therapy was demonstrated by reduction of new S. aureus intramammary infections (IMI caused by the dominant strain type in both herds. Strain typing of representative isolates taken over the duration of all IMI, including pre- and post-treatment isolates, provided more precise estimates of new infection, cure, and re-infection rates. New S. aureus infections in recovered susceptible quarters and the emergence of a new strain type in one herd influenced incidence measures. Conclusion In addition to demonstrating positive direct effects of lactation therapy, this study provides evidence that treatment of subclinical S. aureus mastitis during lactation can
Electron beam dynamics in an ultrafast transmission electron microscope with Wehnelt electrode.
Bücker, K; Picher, M; Crégut, O; LaGrange, T; Reed, B W; Park, S T; Masiel, D J; Banhart, F
2016-12-01
High temporal resolution transmission electron microscopy techniques have shown significant progress in recent years. Using photoelectron pulses induced by ultrashort laser pulses on the cathode, these methods can probe ultrafast materials processes and have revealed numerous dynamic phenomena at the nanoscale. Most recently, the technique has been implemented in standard thermionic electron microscopes that provide a flexible platform for studying material's dynamics over a wide range of spatial and temporal scales. In this study, the electron pulses in such an ultrafast transmission electron microscope are characterized in detail. The microscope is based on a thermionic gun with a Wehnelt electrode and is operated in a stroboscopic photoelectron mode. It is shown that the Wehnelt bias has a decisive influence on the temporal and energy spread of the picosecond electron pulses. Depending on the shape of the cathode and the cathode-Wehnelt distance, different emission patterns with different pulse parameters are obtained. The energy spread of the pulses is determined by space charge and Boersch effects, given by the number of electrons in a pulse. However, filtering effects due to the chromatic aberrations of the Wehnelt electrode allow the extraction of pulses with narrow energy spreads. The temporal spread is governed by electron trajectories of different length and in different electrostatic potentials. High temporal resolution is obtained by excluding shank emission from the cathode and aberration-induced halos in the emission pattern. By varying the cathode-Wehnelt gap, the Wehnelt bias, and the number of photoelectrons in a pulse, tradeoffs between energy and temporal resolution as well as beam intensity can be made as needed for experiments. Based on the characterization of the electron pulses, the optimal conditions for the operation of ultrafast TEMs with thermionic gun assembly are elaborated. Copyright © 2016 Elsevier B.V. All rights reserved.
Models to capture the potential for disease transmission in domestic sheep flocks.
Schley, David; Whittle, Sophie; Taylor, Michael; Kiss, Istvan Zoltan
2012-09-15
Successful control of livestock diseases requires an understanding of how they spread amongst animals and between premises. Mathematical models can offer important insight into the dynamics of disease, especially when built upon experimental and/or field data. Here the dynamics of a range of epidemiological models are explored in order to determine which models perform best in capturing real-world heterogeneities at sufficient resolution. Individual based network models are considered together with one- and two-class compartmental models, for which the final epidemic size is calculated as a function of the probability of disease transmission occurring during a given physical contact between two individuals. For numerical results the special cases of a viral disease with a fast recovery rate (foot-and-mouth disease) and a bacterial disease with a slow recovery rate (brucellosis) amongst sheep are considered. Quantitative results from observational studies of physical contact amongst domestic sheep are applied and results from the differently structured flocks (ewes with newborn lambs, ewes with nearly weaned lambs and ewes only) compared. These indicate that the breeding cycle leads to significant changes in the expected basic reproduction ratio of diseases. The observed heterogeneity of contacts amongst animals is best captured by full network simulations, although simple compartmental models describe the key features of an outbreak but, as expected, often overestimate the speed of an outbreak. Here the weights of contacts are heterogeneous, with many low weight links. However, due to the well-connected nature of the networks, this has little effect and differences between models remain small. These results indicate that simple compartmental models can be a useful tool for modelling real-world flocks; their applicability will be greater still for more homogeneously mixed livestock, which could be promoted by higher intensity farming practices. Copyright © 2012
International Nuclear Information System (INIS)
Shin, Seung Ki; Seong, Poong Hyun
2008-01-01
Conventional static reliability analysis methods are inadequate for modeling dynamic interactions between components of a system. Various techniques such as dynamic fault tree, dynamic Bayesian networks, and dynamic reliability block diagrams have been proposed for modeling dynamic systems based on improvement of the conventional modeling methods. In this paper, we review these methods briefly and introduce dynamic nodes to the existing Reliability Graph with General Gates (RGGG) as an intuitive modeling method to model dynamic systems. For a quantitative analysis, we use a discrete-time method to convert an RGGG to an equivalent Bayesian network and develop a software tool for generation of probability tables
Barberis Rami, Matías Ezequiel; Berić, Dejan; Mátai, Anikó; Opriş, Lavinia-Ioana; Ricci, Giulia; Rustja, Dritan
2015-01-01
The project aims to promote and preserve both tangible and intangible cultural heritage in a particular region of the Danube river basin, Tisza Region (TR). The TR cultural heritage is less-well-known in the rest of Europe and is at risk of being lost or forgotten if not preserved and supported. In this project is presented an innovative and strategic bottom-up model which allows local people to manage how their heritage is disseminated through transmission and promotion of their ...
Altered vector competence in an experimental mosquito-mouse transmission model of Zika infection.
Directory of Open Access Journals (Sweden)
Ryuta Uraki
2018-03-01
Full Text Available Few animal models of Zika virus (ZIKV infection have incorporated arthropod-borne transmission. Here, we establish an Aedes aegypti mosquito model of ZIKV infection of mice, and demonstrate altered vector competency among three strains, (Orlando, ORL, Ho Chi Minh, HCM, and Patilas, PAT. All strains acquired ZIKV in their midguts after a blood meal from infected mice, but ZIKV transmission only occurred in mice fed upon by HCM, and to a lesser extent PAT, but not ORL, mosquitoes. This defect in transmission from ORL or PAT mosquitoes was overcome by intrathoracic injection of ZIKV into mosquito. Genetic analysis revealed significant diversity among these strains, suggesting a genetic basis for differences in ability for mosquito strains to transmit ZIKV. The intrathoracic injection mosquito-mouse transmission model is critical to understanding the influence of mosquitoes on ZIKV transmission, infectivity and pathogenesis in the vertebrate host, and represents a natural transmission route for testing vaccines and therapeutics.
Directory of Open Access Journals (Sweden)
P. Lemieux-Mellouki
2017-12-01
Conclusions: Modelling genital-site only transmission may overestimate vaccination impact if extragenital infections contribute to systemic natural immunity or underestimate vaccination impact if a high proportion of genital infections originate from extragenital infections. Under current understanding of heterosexual HPV transmission and immunity, a substantial bias from using uni-site models in predicting vaccination effectiveness against genital HPV infection is unlikely to occur.
Collins, K.A.; Wang, C.Y.; Adams, M.; Mitchell, H.; Rampton, M.; Elliott, S.; Reuling, I.J.; Bousema, T.; Sauerwein, R.; Chalon, S.; Mohrle, J.J.; McCarthy, J.S.
2018-01-01
BACKGROUND: Drugs and vaccines that can interrupt the transmission of Plasmodium falciparum will be important for malaria control and elimination. However, models for early clinical evaluation of candidate transmission-blocking interventions are currently unavailable. Here, we describe a new model
Characterizing and modeling citation dynamics.
Directory of Open Access Journals (Sweden)
Young-Ho Eom
Full Text Available Citation distributions are crucial for the analysis and modeling of the activity of scientists. We investigated bibliometric data of papers published in journals of the American Physical Society, searching for the type of function which best describes the observed citation distributions. We used the goodness of fit with Kolmogorov-Smirnov statistics for three classes of functions: log-normal, simple power law and shifted power law. The shifted power law turns out to be the most reliable hypothesis for all citation networks we derived, which correspond to different time spans. We find that citation dynamics is characterized by bursts, usually occurring within a few years since publication of a paper, and the burst size spans several orders of magnitude. We also investigated the microscopic mechanisms for the evolution of citation networks, by proposing a linear preferential attachment with time dependent initial attractiveness. The model successfully reproduces the empirical citation distributions and accounts for the presence of citation bursts as well.
Supply based on demand dynamical model
Levi, Asaf; Sabuco, Juan; Sanjuán, Miguel A. F.
2018-04-01
We propose and numerically analyze a simple dynamical model that describes the firm behaviors under uncertainty of demand. Iterating this simple model and varying some parameter values, we observe a wide variety of market dynamics such as equilibria, periodic, and chaotic behaviors. Interestingly, the model is also able to reproduce market collapses.
Opinion dynamics model based on quantum formalism
Energy Technology Data Exchange (ETDEWEB)
Artawan, I. Nengah, E-mail: nengahartawan@gmail.com [Theoretical Physics Division, Department of Physics, Udayana University (Indonesia); Trisnawati, N. L. P., E-mail: nlptrisnawati@gmail.com [Biophysics, Department of Physics, Udayana University (Indonesia)
2016-03-11
Opinion dynamics model based on quantum formalism is proposed. The core of the quantum formalism is on the half spin dynamics system. In this research the implicit time evolution operators are derived. The analogy between the model with Deffuant dan Sznajd models is discussed.
Wang, Yishan; Doleschel, Sammy; Wunderlich, Ralf; Heinen, Stefan
2015-03-01
This paper presents a wearable wireless ECG monitoring system based on novel 3-Lead electrode placements for long-term homecare. The experiment for novel 3-Lead electrode placements is carried out, and the results show that the distance between limb electrodes can be significantly reduced. Based on the new electrode position, a small size sensor node, which is powered by a rechargeable battery, is designed to detect, amplify, filter and transmit the ECG signals. The coordinator receives the data and sends it to PC. Finally the signals are displayed on the GUI. In order to control the power consumption of sensor node, a dynamic power adjustment method is applied to automatically adjust the transmission power of the sensor node according to the received signal strength indicator (RSSI), which is related to the distance and obstacle between sensor node and coordinator. The system is evaluated when the user, who wears the sensor, is walking and running. A promising performance is achieved even under body motion. The power consumption can be significantly reduced with this dynamic power adjustment method.
Energy Technology Data Exchange (ETDEWEB)
Armstrong, Michael R. [Materials Science and Technology Division, Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, P.O. Box 808, L-356, Livermore, CA 94550 (United States)], E-mail: armstrong30@llnl.gov; Boyden, Ken [Materials Science and Technology Division, Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, P.O. Box 808, L-356, Livermore, CA 94550 (United States); Browning, Nigel D. [Materials Science and Technology Division, Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, P.O. Box 808, L-356, Livermore, CA 94550 (United States); Department of Chemical Engineering and Materials Science, University of California-Davis, One Shields Avenue, Davis, CA 95616 (United States); Campbell, Geoffrey H.; Colvin, Jeffrey D.; De Hope, William J.; Frank, Alan M. [Materials Science and Technology Division, Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, P.O. Box 808, L-356, Livermore, CA 94550 (United States); Gibson, David J.; Hartemann, Fred [N Division, Physics and Advanced Technologies Directorate, Lawrence Livermore National Laboratory, P.O. Box 808, L-280, Livermore, CA 94550 (United States); Kim, Judy S. [Materials Science and Technology Division, Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, P.O. Box 808, L-356, Livermore, CA 94550 (United States); Department of Chemical Engineering and Materials Science, University of California-Davis, One Shields Avenue, Davis, CA 95616 (United States); King, Wayne E.; La Grange, Thomas B.; Pyke, Ben J.; Reed, Bryan W.; Shuttlesworth, Richard M.; Stuart, Brent C.; Torralva, Ben R. [Materials Science and Technology Division, Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, P.O. Box 808, L-356, Livermore, CA 94550 (United States)
2007-04-15
Although recent years have seen significant advances in the spatial resolution possible in the transmission electron microscope (TEM), the temporal resolution of most microscopes is limited to video rate at best. This lack of temporal resolution means that our understanding of dynamic processes in materials is extremely limited. High temporal resolution in the TEM can be achieved, however, by replacing the normal thermionic or field emission source with a photoemission source. In this case the temporal resolution is limited only by the ability to create a short pulse of photoexcited electrons in the source, and this can be as short as a few femtoseconds. The operation of the photo-emission source and the control of the subsequent pulse of electrons (containing as many as 5x10{sup 7} electrons) create significant challenges for a standard microscope column that is designed to operate with a single electron in the column at any one time. In this paper, the generation and control of electron pulses in the TEM to obtain a temporal resolution <10{sup -6} s will be described and the effect of the pulse duration and current density on the spatial resolution of the instrument will be examined. The potential of these levels of temporal and spatial resolution for the study of dynamic materials processes will also be discussed.
International Nuclear Information System (INIS)
Armstrong, Michael R.; Boyden, Ken; Browning, Nigel D.; Campbell, Geoffrey H.; Colvin, Jeffrey D.; De Hope, William J.; Frank, Alan M.; Gibson, David J.; Hartemann, Fred; Kim, Judy S.; King, Wayne E.; La Grange, Thomas B.; Pyke, Ben J.; Reed, Bryan W.; Shuttlesworth, Richard M.; Stuart, Brent C.; Torralva, Ben R.
2007-01-01
Although recent years have seen significant advances in the spatial resolution possible in the transmission electron microscope (TEM), the temporal resolution of most microscopes is limited to video rate at best. This lack of temporal resolution means that our understanding of dynamic processes in materials is extremely limited. High temporal resolution in the TEM can be achieved, however, by replacing the normal thermionic or field emission source with a photoemission source. In this case the temporal resolution is limited only by the ability to create a short pulse of photoexcited electrons in the source, and this can be as short as a few femtoseconds. The operation of the photo-emission source and the control of the subsequent pulse of electrons (containing as many as 5x10 7 electrons) create significant challenges for a standard microscope column that is designed to operate with a single electron in the column at any one time. In this paper, the generation and control of electron pulses in the TEM to obtain a temporal resolution -6 s will be described and the effect of the pulse duration and current density on the spatial resolution of the instrument will be examined. The potential of these levels of temporal and spatial resolution for the study of dynamic materials processes will also be discussed
Relating structure and dynamics in organisation models
Jonker, C.M.; Treur, J.
2003-01-01
To understand how an organisational structure relates to dynamics is an interesting fundamental challenge in the area of social modelling. Specifications of organisational structure usually have a diagrammatic form that abstracts from more detailed dynamics. Dynamic properties of agent systems, on
Spatiotemporal Dynamics of Scrub Typhus Transmission in Mainland China, 2006-2014.
Wu, Yi-Cheng; Qian, Quan; Soares Magalhaes, Ricardo J; Han, Zhi-Hai; Hu, Wen-Biao; Haque, Ubydul; Weppelmann, Thomas A; Wang, Yong; Liu, Yun-Xi; Li, Xin-Lou; Sun, Hai-Long; Sun, Yan-Song; Clements, Archie C A; Li, Shen-Long; Zhang, Wen-Yi
2016-08-01
Scrub typhus is endemic in the Asia-Pacific region including China, and the number of reported cases has increased dramatically in the past decade. However, the spatial-temporal dynamics and the potential risk factors in transmission of scrub typhus in mainland China have yet to be characterized. This study aims to explore the spatiotemporal dynamics of reported scrub typhus cases in mainland China between January 2006 and December 2014, to detect the location of high risk spatiotemporal clusters of scrub typhus cases, and identify the potential risk factors affecting the re-emergence of the disease. Monthly cases of scrub typhus reported at the county level between 2006 and 2014 were obtained from the Chinese Center for Diseases Control and Prevention. Time-series analyses, spatiotemporal cluster analyses, and spatial scan statistics were used to explore the characteristics of the scrub typhus incidence. To explore the association between scrub typhus incidence and environmental variables panel Poisson regression analysis was conducted. During the time period between 2006 and 2014 a total of 54,558 scrub typhus cases were reported in mainland China, which grew exponentially. The majority of cases were reported each year between July and November, with peak incidence during October every year. The spatiotemporal dynamics of scrub typhus varied over the study period with high-risk clusters identified in southwest, southern, and middle-eastern part of China. Scrub typhus incidence was positively correlated with the percentage of shrub and meteorological variables including temperature and precipitation. The results of this study demonstrate areas in China that could be targeted with public health interventions to mitigate the growing threat of scrub typhus in the country.
A Multi-objective Model for Transmission Planning Under Uncertainties
DEFF Research Database (Denmark)
Zhang, Chunyu; Wang, Qi; Ding, Yi
2014-01-01
The significant growth of distributed energy resources (DERs) associated with smart grid technologies has prompted excessive uncertainties in the transmission system. The most representative is the novel notation of commercial aggregator who has lighted a bright way for DERs to participate power...
Tuberculosis in a South African prison – a transmission modelling ...
African Journals Online (AJOL)
Background. Prisons are recognised internationally as institutions with very high tuberculosis (TB) burdens where transmission is predominantly determined by contact between infectious and susceptible prisoners. A recent South African court case described the conditions under which prisoners awaiting trial were kept.
Dynamics of forest malaria transmission in Balaghat district, Madhya Pradesh, India.
Directory of Open Access Journals (Sweden)
Neeru Singh
Full Text Available BACKGROUND: An epidemiological and entomological study was carried out in Balaghat district, Madhya Pradesh, India to understand the dynamics of forest malaria transmission in a difficult and hard to reach area where indoor residual spray and insecticide treated nets were used for vector control. METHODS: This community based cross-sectional study was undertaken from January 2010 to December 2012 in Baihar and Birsa Community Health Centres of district Balaghat for screening malaria cases. Entomological surveillance included indoor resting collections, pyrethrum spray catches and light trap catches. Anophelines were assayed by ELISA for detection of Plasmodium circumsporozoite protein. FINDINGS: Plasmodium falciparum infection accounted for >80% of all infections. P. vivax 16.5%, P. malariae 0.75% and remaining were mixed infections of P. falciparum, P. vivax and P. malariae. More than, 30% infections were found in infants under 6 months of age. Overall, an increasing trend in malaria positivity was observed from 2010 to 2012 (chi-square for trend = 663.55; P<0.0001. Twenty five Anopheles culicifacies (sibling species C, D and E were positive for circumsporozoite protein of P. falciparum (44% and P. vivax (56%. Additionally, 2 An. fluviatilis, were found positive for P. falciparum and 1 for P. vivax (sibling species S and T. An. fluviatilis sibling species T was found as vector in forest villages for the first time in India. CONCLUSION: These results showed that the study villages are experiencing almost perennial malaria transmission inspite of indoor residual spray and insecticide treated nets. Therefore, there is a need for new indoor residual insecticides which has longer residual life or complete coverage of population with long lasting insecticide treated nets or both indoor residual spray and long lasting bed nets for effective vector control. There is a need to undertake a well designed case control study to evaluate the efficacy
DEFF Research Database (Denmark)
Hansen, Thomas Willum; Dunin-Borkowski, Rafal E.; Wagner, Jakob Birkedal
resulting in the formation of larger particles and a loss of catalytic performance. Several models of sintering in different systems have been put forward [1,2]. However, most investigations have been post mortem studies, revealing only the final state of the catalyst. Transmission electron microscopy (TEM....... The combined capabilities of ETEM and image CS correction provide unique possibilities to study this relationship. However, in order to fully quantify image contrast from such experiments, a deeper understanding of the scattering of fast electrons in the presence of gas molecules in the pole piece gap...... of the microscope is needed. As industrial catalysts are usually complex high surface area materials, they are often not suited for fundamental studies. For this purpose, model systems consisting of gold nanoparticles on sheets of low surface area boron nitride and graphite supports were produced. Sheets...
Bhumiratana, Adisak; Intarapuk, Apiradee; Sorosjinda-Nunthawarasilp, Prapa; Maneekan, Pannamas; Koyadun, Surachart
2013-01-01
This systematic review elaborates the concepts and impacts of border malaria, particularly on the emergence and spread of Plasmodium falciparum and Plasmodium vivax multidrug resistance (MDR) malaria on Thailand-Myanmar and Thailand-Cambodia borders. Border malaria encompasses any complex epidemiological settings of forest-related and forest fringe-related malaria, both regularly occurring in certain transmission areas and manifesting a trend of increased incidence in transmission prone areas along these borders, as the result of interconnections of human settlements and movement activities, cross-border population migrations, ecological changes, vector population dynamics, and multidrug resistance. For regional and global perspectives, this review analyzes and synthesizes the rationales pertaining to transmission dynamics and the vulnerabilities of border malaria that constrain surveillance and control of the world's most MDR falciparum and vivax malaria on these chaotic borders. PMID:23865048
Directory of Open Access Journals (Sweden)
Adisak Bhumiratana
2013-01-01
Full Text Available This systematic review elaborates the concepts and impacts of border malaria, particularly on the emergence and spread of Plasmodium falciparum and Plasmodium vivax multidrug resistance (MDR malaria on Thailand-Myanmar and Thailand-Cambodia borders. Border malaria encompasses any complex epidemiological settings of forest-related and forest fringe-related malaria, both regularly occurring in certain transmission areas and manifesting a trend of increased incidence in transmission prone areas along these borders, as the result of interconnections of human settlements and movement activities, cross-border population migrations, ecological changes, vector population dynamics, and multidrug resistance. For regional and global perspectives, this review analyzes and synthesizes the rationales pertaining to transmission dynamics and the vulnerabilities of border malaria that constrain surveillance and control of the world’s most MDR falciparum and vivax malaria on these chaotic borders.
Marion, Estelle; Eyangoh, Sara; Yeramian, Edouard; Doannio, Julien; Landier, Jordi; Aubry, Jacques; Fontanet, Arnaud; Rogier, Christophe; Cassisa, Viviane; Cottin, Jane; Marot, Agnès; Eveillard, Matthieu; Kamdem, Yannick; Legras, Pierre; Deshayes, Caroline; Saint-André, Jean-Paul; Marsollier, Laurent
2010-07-06
Buruli ulcer, the third mycobacterial disease after tuberculosis and leprosy, is caused by the environmental mycobacterium M. ulcerans. Various modes of transmission have been suspected for this disease, with no general consensus acceptance for any of them up to now. Since laboratory models demonstrated the ability of water bugs to transmit M. ulcerans, a particular attention is focused on the transmission of the bacilli by water bugs as hosts and vectors. However, it is only through detailed knowledge of the biodiversity and ecology of water bugs that the importance of this mode of transmission can be fully assessed. It is the objective of the work here to decipher the role of water bugs in M. ulcerans ecology and transmission, based on large-scale field studies. The distribution of M. ulcerans-hosting water bugs was monitored on previously unprecedented time and space scales: a total of 7,407 water bugs, belonging to large number of different families, were collected over one year, in Buruli ulcer endemic and non endemic areas in central Cameroon. This study demonstrated the presence of M. ulcerans in insect saliva. In addition, the field results provided a full picture of the ecology of transmission in terms of biodiversity and detailed specification of seasonal and regional dynamics, with large temporal heterogeneity in the insect tissue colonization rate and detection of M. ulcerans only in water bug tissues collected in Buruli ulcer endemic areas. The large-scale detection of bacilli in saliva of biting water bugs gives enhanced weight to their role in M. ulcerans transmission. On practical grounds, beyond the ecological interest, the results concerning seasonal and regional dynamics can provide an efficient tool in the hands of sanitary authorities to monitor environmental risks associated with Buruli ulcer.
Ngo Xuan, T.; Verreth, J.A.J.; Vlak, J.M.; Jong, de M.C.M.
2014-01-01
White spot syndrome virus (WSSV), a rod-shaped double-stranded DNA virus, is an infectious agent causing fatal disease in shrimp farming around the globe. Within shrimp populations WSSV is transmitted very fast, however, the modes and dynamics of transmission of this virus are not well understood.
DEFF Research Database (Denmark)
Ding, Tao; Li, Cheng; Huang, Can
2018-01-01
–slave structure and improves traditional centralized modeling methods by alleviating the big data problem in a control center. Specifically, the transmission-distribution-network coordination issue of the hierarchical modeling method is investigated. First, a curve-fitting approach is developed to provide a cost......In order to solve the reactive power optimization with joint transmission and distribution networks, a hierarchical modeling method is proposed in this paper. It allows the reactive power optimization of transmission and distribution networks to be performed separately, leading to a master...... optimality. Numerical results on two test systems verify the effectiveness of the proposed hierarchical modeling and curve-fitting methods....
Communicative Modelling of Cultural Transmission and Evolution Through a Holographic Cognition Model
Directory of Open Access Journals (Sweden)
Ambjörn Naeve
2012-12-01
Full Text Available This article presents communicative ways to model the transmission and evolution of the processes and artefacts of a culture as the result of ongoing interactions between its members - both at the tacit and the explicit level. The purpose is not to model the entire cultural process, but to provide semantically rich “conceptual placeholders” for modelling any cultural activity that is considered important enough within a certain context. The general purpose of communicative modelling is to create models that improve the quality of communication between people. In order to capture the subjective aspects of Gregory Bateson’s definition of information as “a difference that makes a difference,” the article introduces a Holographic Cognition Model that uses optical holography as an analogy for human cognition, with the object beam of holography corresponding to the first difference (the situation that the cognitive agent encounters, and the reference beam of holography corresponding to the subjective experiences and biases that the agent brings to the situation, and which makes the second difference (the interference/interpretation pattern unique for each agent. By combining the HCM with a semantically rich and recursive form of process modelling, based on the SECI-theory of knowledge creation, we arrive at way to model the cultural transmission and evolution process that is consistent with the Unified Theory of Information (the Triple-C model with its emphasis on intra-, inter- and supra-actions.
Directory of Open Access Journals (Sweden)
Cara E. Brook
2017-09-01
Full Text Available Bartonella spp. are erythrocytic bacteria transmitted via arthropod vectors, which infect a broad range of vertebrate hosts, including humans. We investigated transmission dynamics and host-parasite-vector relationships for potentially zoonotic Bartonella spp. in invasive Rattus rattus hosts and associated arthropod ectoparasites in Madagascar. We identified five distinct species of Bartonella (B. elizabethae 1, B. elizabethae 2, B. phoceensis 1, B. rattimassiliensis 1, and B. tribocorum 1 infecting R. rattus rodents and their ectoparasites. We fit standard epidemiological models to species-specific age-prevalence data for the four Bartonella spp. with sufficient data, thus quantifying age-structured force of infection. Known zoonotic agents, B. elizabethae 1 and 2, were best described by models exhibiting high forces of infection in early age class individuals and allowing for recovery from infection, while B. phoceensis 1 and B. rattimassiliensis 1 were best fit by models of lifelong infection without recovery and substantially lower forces of infection. Nested sequences of B. elizabethae 1 and 2 were recovered from rodent hosts and their Synopsyllus fonquerniei and Xenopsylla cheopsis fleas, with a particularly high prevalence in the outdoor-dwelling, highland-endemic S. fonquerniei. These findings expand on force of infection analyses to elucidate the ecological niche of the zoonotic Bartonella elizabethae complex in Madagascar, hinting at a potential vector role for S. fonquerniei. Our analyses underscore the uniqueness of such ecologies for Bartonella species, which pose a variable range of potential zoonotic threats.
Electron beam dynamics in an ultrafast transmission electron microscope with Wehnelt electrode
Energy Technology Data Exchange (ETDEWEB)
Bücker, K.; Picher, M.; Crégut, O. [Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, 67034 Strasbourg (France); LaGrange, T. [Interdisciplinary Centre for Electron Microscopy, École Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland); Reed, B.W.; Park, S.T.; Masiel, D.J. [Integrated Dynamic Electron Solutions, Inc., 5653 Stoneridge Drive 117, Pleasanton, CA 94588 (United States); Banhart, F., E-mail: florian.banhart@ipcms.unistra.fr [Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, 67034 Strasbourg (France)
2016-12-15
High temporal resolution transmission electron microscopy techniques have shown significant progress in recent years. Using photoelectron pulses induced by ultrashort laser pulses on the cathode, these methods can probe ultrafast materials processes and have revealed numerous dynamic phenomena at the nanoscale. Most recently, the technique has been implemented in standard thermionic electron microscopes that provide a flexible platform for studying material's dynamics over a wide range of spatial and temporal scales. In this study, the electron pulses in such an ultrafast transmission electron microscope are characterized in detail. The microscope is based on a thermionic gun with a Wehnelt electrode and is operated in a stroboscopic photoelectron mode. It is shown that the Wehnelt bias has a decisive influence on the temporal and energy spread of the picosecond electron pulses. Depending on the shape of the cathode and the cathode-Wehnelt distance, different emission patterns with different pulse parameters are obtained. The energy spread of the pulses is determined by space charge and Boersch effects, given by the number of electrons in a pulse. However, filtering effects due to the chromatic aberrations of the Wehnelt electrode allow the extraction of pulses with narrow energy spreads. The temporal spread is governed by electron trajectories of different length and in different electrostatic potentials. High temporal resolution is obtained by excluding shank emission from the cathode and aberration-induced halos in the emission pattern. By varying the cathode-Wehnelt gap, the Wehnelt bias, and the number of photoelectrons in a pulse, tradeoffs between energy and temporal resolution as well as beam intensity can be made as needed for experiments. Based on the characterization of the electron pulses, the optimal conditions for the operation of ultrafast TEMs with thermionic gun assembly are elaborated. - Highlights: • A detailed characterization of electron
Dynamic modelling of nuclear steam generators
International Nuclear Information System (INIS)
Kerlin, T.W.; Katz, E.M.; Freels, J.; Thakkar, J.
1980-01-01
Moving boundary, nodal models with dynamic energy balances, dynamic mass balances, quasi-static momentum balances, and an equivalent single channel approach have been developed for steam generators used in nuclear power plants. The model for the U-tube recirculation type steam generator is described and comparisons are made of responses from models of different complexity; non-linear versus linear, high-order versus low order, detailed modeling of the control system versus a simple control assumption. The results of dynamic tests on nuclear power systems show that when this steam generator model is included in a system simulation there is good agreement with actual plant performance. (author)
Dynamic Airspace Managment - Models and Algorithms
Cheng, Peng; Geng, Rui
2010-01-01
This chapter investigates the models and algorithms for implementing the concept of Dynamic Airspace Management. Three models are discussed. First two models are about how to use or adjust air route dynamically in order to speed up air trafï¬c ï¬‚ow and reduce delay. The third model gives a way to dynamically generate the optimal sector conï¬guration for an air trafï¬c control center to both balance the controllerâ€™s workload and save control resources. The ï¬rst model, called the Dynami...
Wind Farm Decentralized Dynamic Modeling With Parameters
DEFF Research Database (Denmark)
Soltani, Mohsen; Shakeri, Sayyed Mojtaba; Grunnet, Jacob Deleuran
2010-01-01
Development of dynamic wind flow models for wind farms is part of the research in European research FP7 project AEOLUS. The objective of this report is to provide decentralized dynamic wind flow models with parameters. The report presents a structure for decentralized flow models with inputs from...... local models. The results of this report are especially useful, but not limited, to design a decentralized wind farm controller, since in centralized controller design one can also use the model and update it in a central computing node.......Development of dynamic wind flow models for wind farms is part of the research in European research FP7 project AEOLUS. The objective of this report is to provide decentralized dynamic wind flow models with parameters. The report presents a structure for decentralized flow models with inputs from...
System dynamics modelling of situation awareness
CSIR Research Space (South Africa)
Oosthuizen, R
2015-11-01
Full Text Available . The feedback loops and delays in the Command and Control system also contribute to the complex dynamic behavior. This paper will build on existing situation awareness models to develop a System Dynamics model to support a qualitative investigation through...
An Agent Model Integrating an Adaptive Model for Environmental Dynamics
Treur, J.; Umair, M.
2011-01-01
The environments in which agents are used often may be described by dynamical models, e.g., in the form of a set of differential equations. In this paper, an agent model is proposed that can perform model-based reasoning about the environment, based on a numerical (dynamical system) model of the
Hydration dynamics near a model protein surface
International Nuclear Information System (INIS)
Russo, Daniela; Hura, Greg; Head-Gordon, Teresa
2003-01-01
The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces
Secundino, Nagila Francinete Costa; Chaves, Barbara Aparecida; Orfano, Alessandra Silva; Silveira, Karine Renata Dias; Rodrigues, Nilton Barnabe; Campolina, Thais Bonifácio; Nacif-Pimenta, Rafael; Villegas, Luiz Eduardo Martinez; Silva, Breno Melo; Lacerda, Marcus Vinícius Guimarães; Norris, Douglas Eric; Pimenta, Paulo Filemon Paolucci
2017-07-20
Zika disease has transformed into a serious global health problem due to the rapid spread of the arbovirus and alarming severity including congenital complications, microcephaly and Guillain-Barré syndrome. Zika virus (ZIKV) is primarily transmitted to humans through the bite of an infective mosquito, with Aedes aegypti being the main vector. We successfully developed a ZIKV experimental transmission model by single infectious Ae. aegypti bite to a laboratory mouse using circulating Brazilian strains of both arbovirus and vector. Mosquitoes were orally infected and single Ae. aegypti were allowed to feed on mouse ears 14 days post-infection. Additionally, salivary gland (SG) homogenates from infected mosquitoes were intrathoracically inoculated into naïve Ae. aegypti. Mosquito and mouse tissue samples were cultured in C6/36 cells and processed by quantitative real-time PCR. A total of 26 Ae. aegypti were allowed to feed individually on mouse ears. Of these, 17 mosquitoes fed, all to full engorgement. The transmission rate of ZIKV by bite from these engorged mosquitoes to mouse ears was 100%. The amount of virus inoculated into the ears by bites ranged from 2 × 10 2 -2.1 × 10 10 ZIKV cDNA copies and was positively correlated with ZIKV cDNA quantified from SGs dissected from mosquitoes post-feeding. Replicating ZIKV was confirmed in macerated SGs (2.45 × 10 7 cDNA copies), mouse ear tissue (1.15 × 10 3 cDNA copies, and mosquitoes 14 days post-intrathoracic inoculation (1.49 × 10 7 cDNA copies) by cytopathic effect in C6/36 cell culture and qPCR. Our model illustrates successful transmission of ZIKV by an infectious mosquito bite to a live vertebrate host. This approach offers a comprehensive tool for evaluating the development of infection in and transmission from mosquitoes, and the vertebrate-ZIKV interaction and progression of infection following a natural transmission process.
An optimal control strategies using vaccination and fogging in dengue fever transmission model
Fitria, Irma; Winarni, Pancahayani, Sigit; Subchan
2017-08-01
This paper discussed regarding a model and an optimal control problem of dengue fever transmission. We classified the model as human and vector (mosquito) population classes. For the human population, there are three subclasses, such as susceptible, infected, and resistant classes. Then, for the vector population, we divided it into wiggler, susceptible, and infected vector classes. Thus, the model consists of six dynamic equations. To minimize the number of dengue fever cases, we designed two optimal control variables in the model, the giving of fogging and vaccination. The objective function of this optimal control problem is to minimize the number of infected human population, the number of vector, and the cost of the controlling efforts. By giving the fogging optimally, the number of vector can be minimized. In this case, we considered the giving of vaccination as a control variable because it is one of the efforts that are being developed to reduce the spreading of dengue fever. We used Pontryagin Minimum Principle to solve the optimal control problem. Furthermore, the numerical simulation results are given to show the effect of the optimal control strategies in order to minimize the epidemic of dengue fever.
Natural gas transmission and distribution model of the National Energy Modeling System
International Nuclear Information System (INIS)
1997-02-01
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of Integrated Analysis and Forecasting of the Energy Information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. From 1982 through 1993, the Intermediate Future Forecasting System (IFFS) was used by the EIA for its analyses, and the Gas Analysis Modeling System (GAMS) was used within IFFS to represent natural gas markets. Prior to 1982, the Midterm Energy Forecasting System (MEFS), also referred to as the Project Independence Evaluation System (PIES), was employed. NEMS was developed to enhance and update EIA's modeling capability by internally incorporating models of energy markets that had previously been analyzed off-line. In addition, greater structural detail in NEMS permits the analysis of a broader range of energy issues. The time horizon of NEMS is the midterm period (i.e., through 2015). In order to represent the regional differences in energy markets, the component models of NEMS function at regional levels appropriate for the markets represented, with subsequent aggregation/disaggregation to the Census Division level for reporting purposes
Natural gas transmission and distribution model of the National Energy Modeling System
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-02-01
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of Integrated Analysis and Forecasting of the Energy Information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. From 1982 through 1993, the Intermediate Future Forecasting System (IFFS) was used by the EIA for its analyses, and the Gas Analysis Modeling System (GAMS) was used within IFFS to represent natural gas markets. Prior to 1982, the Midterm Energy Forecasting System (MEFS), also referred to as the Project Independence Evaluation System (PIES), was employed. NEMS was developed to enhance and update EIA`s modeling capability by internally incorporating models of energy markets that had previously been analyzed off-line. In addition, greater structural detail in NEMS permits the analysis of a broader range of energy issues. The time horizon of NEMS is the midterm period (i.e., through 2015). In order to represent the regional differences in energy markets, the component models of NEMS function at regional levels appropriate for the markets represented, with subsequent aggregation/disaggregation to the Census Division level for reporting purposes.
Issues affecting the electricity transmission system in Mexico under a competitive integrated model
Energy Technology Data Exchange (ETDEWEB)
Avila Rosales, M.A.; Gonzalez Flores, J. [Federal Electricity Commission, Mexico City (Mexico)
2008-07-01
The electricity sector in Mexico is undergoing a process of significant structural change. The traditional industry framework has been exposed to new market structures and greater competition, both of which are being introduced by changing regulations regarding who can generate, transmit, distribute and sell electricity. Mexico's power industry is changing to a competitive integrated model. Electricity industry restructuring is partly based on the assumption that transmission systems should be flexible, reliable, and open to all exchanges no matter where the suppliers and consumers of energy are located and who they are. However, neither the existing transmission systems nor its management infrastructure can fully support this open exchange. This paper described the primary issues affecting the transmission system in Mexico under a competitive environment and a transmission expansion planning approach that took the uncertainties associated with the location and size of new generating power stations into consideration in order to produce least-cost and robust transmission plans. The paper described the planning process, including a rigorous analysis of the economics of the resulting transmission plans. Specifically, the paper described the current regulatory framework and supply adequacy as well as current procedures and methodologies for transmission management and expansion planning. The transmission planning methodology was also presented. This included a minimum cost analysis; profit analysis; and least-cost transmission plan. It was concluded that the transmission expansion planning approach stressed that a horizon year viewpoint was important because transmission additions have long-term use. The transmission expansion planning approach, further defined the process of selecting transmission projects as one of comparing and optimizing attributes such as near-term needs; long-term utilization; contribution to overall reliability; and favorable or least
Forecasting house prices in the 50 states using Dynamic Model Averaging and Dynamic Model Selection
DEFF Research Database (Denmark)
Bork, Lasse; Møller, Stig Vinther
2015-01-01
We examine house price forecastability across the 50 states using Dynamic Model Averaging and Dynamic Model Selection, which allow for model change and parameter shifts. By allowing the entire forecasting model to change over time and across locations, the forecasting accuracy improves substantia......We examine house price forecastability across the 50 states using Dynamic Model Averaging and Dynamic Model Selection, which allow for model change and parameter shifts. By allowing the entire forecasting model to change over time and across locations, the forecasting accuracy improves...
Economics, cultural transmission, and the dynamics of the sex ratio at birth in China.
Lipatov, Mikhail; Li, Shuzhuo; Feldman, Marcus W
2008-12-09
In rural China, the ratio of newborn boys to newborn girls [sex ratio at birth (SRB)] has been rising for several decades, to values significantly above its biological norm. This trend has a number of alarming societal consequences, and has attracted the attention of scholars and politicians. The root of the problem lies in a 2,500-year-old culture of son preference. This culture is intricately linked with the economic reality of each couple's life, so that there are financial and psychological repercussions to parents who have no sons. To bring greater clarity and understanding to this issue, we present a quantitative framework that describes the interaction between economics and cultural transmission. We start with an explicit mechanism by which economic incentives can change cultural beliefs of a given individual, and go on to include a mechanism of cultural inheritance from generation to generation. We then show how economic conditions can affect the dynamics of cultural change in an entire society, and may lead to a decrease in the country's sex ratio at birth.
Multiscale model for pedestrian and infection dynamics during air travel
Namilae, Sirish; Derjany, Pierrot; Mubayi, Anuj; Scotch, Mathew; Srinivasan, Ashok
2017-05-01
In this paper we develop a multiscale model combining social-force-based pedestrian movement with a population level stochastic infection transmission dynamics framework. The model is then applied to study the infection transmission within airplanes and the transmission of the Ebola virus through casual contacts. Drastic limitations on air-travel during epidemics, such as during the 2014 Ebola outbreak in West Africa, carry considerable economic and human costs. We use the computational model to evaluate the effects of passenger movement within airplanes and air-travel policies on the geospatial spread of infectious diseases. We find that boarding policy by an airline is more critical for infection propagation compared to deplaning policy. Enplaning in two sections resulted in fewer infections than the currently followed strategy with multiple zones. In addition, we found that small commercial airplanes are better than larger ones at reducing the number of new infections in a flight. Aggregated results indicate that passenger movement strategies and airplane size predicted through these network models can have significant impact on an event like the 2014 Ebola epidemic. The methodology developed here is generic and can be readily modified to incorporate the impact from the outbreak of other directly transmitted infectious diseases.
Numerical simulation of cathode plasma dynamics in magnetically insulated vacuum transmission lines
International Nuclear Information System (INIS)
Thoma, C.; Genoni, T. C.; Welch, D. R.; Rose, D. V.; Clark, R. E.; Miller, C. L.; Stygar, W. A.; Kiefer, M. L.
2015-01-01
A novel algorithm for the simulation of cathode plasmas in particle-in-cell codes is described and applied to investigate cathode plasma evolution in magnetically insulated transmission lines (MITLs). The MITL electron sheath is modeled by a fully kinetic electron species. Electron and ion macroparticles, both modeled as fluid species, form a dense plasma which is initially localized at the cathode surface. Energetic plasma electron particles can be converted to kinetic electrons to resupply the electron flux at the plasma edge (the “effective” cathode). Using this model, we compare results for the time evolution of the cathode plasma and MITL electron flow with a simplified (isothermal) diffusion model. Simulations in 1D show a slow diffusive expansion of the plasma from the cathode surface. But in multiple dimensions, the plasma can expand much more rapidly due to anomalous diffusion caused by an instability due to the strong coupling of a transverse magnetic mode in the electron sheath with the expanding resistive plasma layer
Adaptive numerical modeling of dynamic crack propagation
International Nuclear Information System (INIS)
Adouani, H.; Tie, B.; Berdin, C.; Aubry, D.
2006-01-01
We propose an adaptive numerical strategy that aims at developing reliable and efficient numerical tools to model dynamic crack propagation and crack arrest. We use the cohesive zone theory as behavior of interface-type elements to model crack. Since the crack path is generally unknown beforehand, adaptive meshing is proposed to model the dynamic crack propagation. The dynamic study requires the development of specific solvers for time integration. As both geometry and finite element mesh of the studied structure evolve in time during transient analysis, the stability behavior of dynamic solver becomes a major concern. For this purpose, we use the space-time discontinuous Galerkin finite element method, well-known to provide a natural framework to manage meshes that evolve in time. As an important result, we prove that the space-time discontinuous Galerkin solver is unconditionally stable, when the dynamic crack propagation is modeled by the cohesive zone theory, which is highly non-linear. (authors)
Modeling effective transmission pathways and control of the world's most successful parasite.
Turner, Matthew; Lenhart, Suzanne; Rosenthal, Benjamin; Zhao, Xiaopeng
2013-06-01
Toxoplasma gondii(T. gondii) is a single-celled, intracellular protozoan responsible for the disease toxoplasmosis. The parasite is prevalent worldwide, and it infects all warm-blooded vertebrates. Consumption of meats in which this parasite has encysted confers risk of infection to people and other animals, as does ingestion of water or foods contaminated with environmentally resistant oocysts excreted by cats. Vertical transmission (from mother to offspring) is also possible, leading to disease risk and contributing additional means of ensuring perpetuation of transmission. In this work, we adopt a differential equation model to investigate the effective transmission pathways of T. gondii, as well as potential control mechanisms. Detailed analyses are carried out to examine the significance of transmission routes, virulence, vertical transmission, parasite-induced changes in host behavior, and controls based on vaccination and harvesting. Modeling and analysis efforts may shed insights into understanding the complex life cycle of T. gondii. Copyright © 2013 Elsevier Inc. All rights reserved.
Nadeau, D.; Isabelle, P. E.; Asselin, M. H.; Parent, A. C.; Jutras, S.; Anctil, F.
2017-12-01
Solar irradiance is the largest driver of land-surface exchanges of energy, water and trace gases. Its absorption by a forest canopy generates considerable sensible and latent heat fluxes as well as tree temperature changes. A fraction of the irradiance gets transmitted through the canopy and powers another layer of energy fluxes, which can reach substantial values. Transmitted radiation is also of particular relevance to understory vegetation photosynthesis, snowpack energetics and soil temperature dynamics. Boreal forest canopy transmissivity needs to be quantified to properly reproduce land-atmosphere interactions in the circumpolar boreal biome, but its high spatiotemporal variability makes it a challenging task. The objective of this study is to characterize the spatiotemporal variability in under-canopy radiation and to evaluate the performance of various models in representing plot-scale observations. The study site is located in Montmorency Forest (47°N, 71°W), in southern Quebec, Canada. The vegetation includes mostly juvenile balsam firs, up to 6 to 8 m tall. Since January 2016, a 15-m flux tower measures the four components of radiation, as well as other relevant fluxes and meteorological variables, on a ≈10° northeast-facing slope. In summer 2016, 20 portable weather stations were mounted in a 150 m x 200 m grid around the flux tower. These stations were equipped with silicon-cell pyranometers and provided measurements of downwelling irradiance at a height of 2 m. This setup allowed us to compute irradiance transmissivity and to assess its spatiotemporal variability at the site. First, we show that the average of daily incoming energy varies tremendously across the sites, from 1 MJ/m2 to nearly 9 MJ/m2, due to large variations in canopy structure over short distances. Using a regression tree analysis, we show that transmissivity mostly depends on sun elevation, diffuse fraction of radiation, sky and sun view fraction and wind speed above canopy. We
Directory of Open Access Journals (Sweden)
Jonathan Mapelli
2010-05-01
Full Text Available Signal elaboration in the cerebellum mossy fiber input pathway presents controversial aspects, especially concerning gain regulation and the spot-like (rather than beam-like appearance of granular-to-molecular layer transmission. By using voltage-sensitive dye (VSD imaging in rat cerebellar slices (Mapelli et al., 2010, we found that mossy fiber bursts optimally excited the granular layer above ~50 Hz and the overlaying molecular layer above ~100 Hz, thus generating a cascade of high-pass filters. NMDA receptors enhanced transmission in the granular, while GABA-A receptors depressed transmission in both the granular and molecular layer. Burst transmission gain was controlled through a dynamic frequency-dependent involvement of these receptors. Moreover, while high-frequency transmission was enhanced along vertical lines connecting the granular to molecular layer, no high-frequency enhancement was observed along the parallel fiber axis in the molecular layer. This was probably due to the stronger effect of Purkinje cell GABA-A receptor-mediated inhibition occurring along the parallel fibers than along the granule cell axon ascending branch. The consequent amplification of burst responses along vertical transmission lines could explain the spot-like activation of Purkinje cells observed following punctuate stimulation in vivo .
Modeling Gas Dynamics in California Sea Lions
2015-09-30
W. and Fahlman, A. (2009). Could beaked whales get the bends?. Effect of diving behaviour and physiology on modelled gas exchange for three species...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Modeling Gas Dynamics in California Sea Lions Andreas...to update a current gas dynamics model with recently acquired data for respiratory compliance (P-V), and body compartment size estimates in
A Dynamic Model of Sustainment Investment
2015-02-01
Sustainment System Dynamics Model 11 Figure 7: Core Structure of Sustainment Work 12 Figure 8: Bandwagon Effect Loop 13 Figure 9: Limits to Growth Loop 14...Dynamics Model sustainment capacity sustainment performance gap Bandwagon Effect R1 Limits to Growth B1 S Work Smarter B3 Work Bigger B2 desired...which is of concern primarily when using the model as a vehicle for research. Figure 8 depicts a reinforcing loop called the “ Bandwagon Effect
Modeling the Dynamic Digestive System Microbiome†
Estes, Anne M.
2015-01-01
“Modeling the Dynamic Digestive System Microbiome” is a hands-on activity designed to demonstrate the dynamics of microbiome ecology using dried pasta and beans to model disturbance events in the human digestive system microbiome. This exercise demonstrates how microbiome diversity is influenced by: 1) niche availability and habitat space and 2) a major disturbance event, such as antibiotic use. Students use a pictorial key to examine prepared models of digestive system microbiomes to determi...
Dynamical patterns of calcium signaling in a functional model of neuron-astrocyte networks
DEFF Research Database (Denmark)
Postnov, D.E.; Koreshkov, R.N.; Brazhe, N.A.
2009-01-01
We propose a functional mathematical model for neuron-astrocyte networks. The model incorporates elements of the tripartite synapse and the spatial branching structure of coupled astrocytes. We consider glutamate-induced calcium signaling as a specific mode of excitability and transmission...... in astrocytic-neuronal networks. We reproduce local and global dynamical patterns observed experimentally....
Dynamic modeling of cost-effectiveness of rotavirus vaccination, Kazakhstan.
Freiesleben de Blasio, Birgitte; Flem, Elmira; Latipov, Renat; Kuatbaeva, Ajnagul; Kristiansen, Ivar Sønbø
2014-01-01
The government of Kazakhstan, a middle-income country in Central Asia, is considering the introduction of rotavirus vaccination into its national immunization program. We performed a cost-effectiveness analysis of rotavirus vaccination spanning 20 years by using a synthesis of dynamic transmission models accounting for herd protection. We found that a vaccination program with 90% coverage would prevent ≈880 rotavirus deaths and save an average of 54,784 life-years for children vaccine cost at vaccination program costs would be entirely offset. To further evaluate efficacy of a vaccine program, benefits of indirect protection conferred by vaccination warrant further study.
Differential equation models for sharp threshold dynamics.
Schramm, Harrison C; Dimitrov, Nedialko B
2014-01-01
We develop an extension to differential equation models of dynamical systems to allow us to analyze probabilistic threshold dynamics that fundamentally and globally change system behavior. We apply our novel modeling approach to two cases of interest: a model of infectious disease modified for malware where a detection event drastically changes dynamics by introducing a new class in competition with the original infection; and the Lanchester model of armed conflict, where the loss of a key capability drastically changes the effectiveness of one of the sides. We derive and demonstrate a step-by-step, repeatable method for applying our novel modeling approach to an arbitrary system, and we compare the resulting differential equations to simulations of the system's random progression. Our work leads to a simple and easily implemented method for analyzing probabilistic threshold dynamics using differential equations. Published by Elsevier Inc.
Nonlinear dynamic phenomena in the beer model
DEFF Research Database (Denmark)
Mosekilde, Erik; Laugesen, Jakob Lund
2007-01-01
The production-distribution system or "beer game" is one of the most well-known system dynamics models. Notorious for the complex dynamics it produces, the beer game has been used for nearly five decades to illustrate how structure generates behavior and to explore human decision making. Here we...
Phone Routing using the Dynamic Memory Model
DEFF Research Database (Denmark)
Bendtsen, Claus Nicolaj; Krink, Thiemo
2002-01-01
In earlier studies a genetic algorithm (GA) extended with the dynamic memory model has shown remarkable performance on real-world-like problems. In this paper we experiment with routing in communication networks and show that the dynamic memory GA performs remarkable well compared to ant colony...
Directory of Open Access Journals (Sweden)
Aleisha R. Brock
2017-05-01
Full Text Available Background: The use of poor quality antimalarial medicines, including the use of non-recommended medicines for treatment such as sulfadoxine-pyrimethamine (SP monotherapy, undermines malaria control and elimination efforts. Furthermore, the use of subtherapeutic doses of the active ingredient(s can theoretically promote the emergence and transmission of drug resistant parasites. Methods: We developed a deterministic compartmental model to quantify the impact of antimalarial medicine quality on the transmission of SP resistance, and validated it using sensitivity analysis and a comparison with data from Kenya collected in 2006. We modelled human and mosquito population dynamics, incorporating two Plasmodium falciparum subtypes (SP-sensitive and SP-resistant and both poor quality and good quality (artemether-lumefantrine antimalarial use. Findings: The model predicted that an increase in human malaria cases, and among these, an increase in the proportion of SP-resistant infections, resulted from an increase in poor quality SP antimalarial use, whether it was full- or half-dose SP monotherapy. Interpretation: Our findings suggest that an increase in poor quality antimalarial use predicts an increase in the transmission of resistance. This highlights the need for stricter control and regulation on the availability and use of poor quality antimalarial medicines, in order to offer safe and effective treatments, and work towards the eradication of malaria. Keywords: Deterministic compartmental model, Falsified antimalarial medicine, Substandard antimalarial treatments, Antimalarial quality, Plasmodium falciparum malaria, Drug resistance
Knell, R J; Begon, M; Thompson, D J
1996-01-22
Central to theoretical studies of host-pathogen population dynamics is a term describing transmission of the pathogen. This usually assumes that transmission is proportional to the density of infectious hosts or particles and of susceptible individuals. We tested this assumption with the bacterial pathogen Bacillus thuringiensis infecting larvae of Plodia interpunctella, the Indian meal moth. Transmission was found to increase in a more than linear way with host density in fourth and fifth instar P. interpunctella, and to decrease with the density of infectious cadavers in the case of fifth instar larvae. Food availability was shown to play an important part in this process. Therefore, on a number of counts, the usual assumption was found not to apply in our experimental system.
Transmission dynamics of rabies virus in Thailand: Implications for disease control
Directory of Open Access Journals (Sweden)
Puanghat Apirom
2005-06-01
Full Text Available Abstract Background In Thailand, rabies remains a neglected disease with authorities continuing to rely on human death statistics while ignoring the financial burden resulting from an enormous increase in post-exposure prophylaxis. Past attempts to conduct a mass dog vaccination and sterilization program have been limited to Bangkok city and have not been successful. We have used molecular epidemiology to define geographic localization of rabies virus phylogroups and their pattern of spread in Thailand. Methods We analyzed 239 nucleoprotein gene sequences from animal and human brain samples collected from all over Thailand between 1998 and 2002. We then reconstructed a phylogenetic tree correlating these data with geographical information. Results All sequences formed a monophyletic tree of 2 distinct phylogroups, TH1 and TH2. Three subgroups were identified in the TH1 subgroup and were distributed in the middle region of the country. Eight subgroups of TH2 viruses were identified widely distributed throughout the country overlapping the TH1 territory. There was a correlation between human-dependent transportation routes and the distribution of virus. Conclusion Inter-regional migration paths of the viruses might be correlated with translocation of dogs associated with humans. Interconnecting factors between human socioeconomic and population density might determine the transmission dynamics of virus in a rural-to-urban polarity. The presence of 2 or more rabies virus groups in a location might be indicative of a gene flow, reflecting a translocation of dogs within such region and adjacent areas. Different approaches may be required for rabies control based on the homo- or heterogeneity of the virus. Areas containing homogeneous virus populations should be targeted first. Control of dog movement associated with humans is essential.
Verza, S G; de Resende, P E; Kaiser, S; Quirici, L; Teixeira, H F; Gosmann, G; Ferreira, F; Ortega, G G
2012-04-01
Entire seeds of Chenopodium quinoa Willd are a rich protein source and are also well-known for their high saponin content. Due to their amphiphily quinoa saponins are able to form intricate micellar aggregates in aqueous media. In this paper we study the aggregates formed by self-association of these compounds from two quinoa saponin fractions (FQ70 and FQ90) as well as several distinctive nanostructures obtained after their complexation with different ratios of cholesterol (CHOL) and phosphatidylcholine (PC). The FQ70 and FQ90 fractions were obtained by reversed-phase preparative chromatography. The structural features of their resulting aggregates were determined by Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Novel nanosized spherical vesicles formed by self-association with mean diameter about 100-200 nm were observed in FQ70 aqueous solutions whereas worm-like micelles an approximate width of 20 nm were detected in FQ90 aqueous solutions. Under experimental conditions similar to those reported for the preparation of Quillaja saponaria ISCOM matrices, tubular and ring-like micelles arose from FQ70:CHOL:PC and FQ90:CHOL:PC formulations, respectively. However, under these conditions no cage-like ISCOM matrices were observed. The saponin composition of FQ70 and FQ90 seems to determine the nanosized structures viewed by TEM. Phytolaccagenic acid, predominant in FQ70 and FQ90 fractions, is accountable for the formation of the nanosized vesicles and tubular structures observed by TEM in the aqueous solutions of both samples. Conversely, ring-like micelles observed in FQ90:CHOL:PC complexes can be attributed to the presence of less polar saponins present in FQ90, in particular those derived from oleanolic acid.
A Transmission-Cost-Based Model to Estimate the Amount of Market-Integrable Wind Resources
DEFF Research Database (Denmark)
Morales González, Juan Miguel; Pinson, Pierre; Madsen, Henrik
2012-01-01
are made to share the expenses in transmission derived from their integration, they may see the doors of electricity markets closed for not being competitive enough. This paper presents a model to decide the amount of wind resources that are economically exploitable at a given location from a transmission......In the pursuit of the large-scale integration of wind power production, it is imperative to evaluate plausible frictions among the stochastic nature of wind generation, electricity markets, and the investments in transmission required to accommodate larger amounts of wind. If wind producers......-cost perspective. This model accounts for the uncertain character of wind by using a modeling framework based on stochastic optimization, simulates market barriers by means of a bi-level structure, and considers the financial risk of investments in transmission through the conditional value-at-risk. The major...
Some dynamical aspects of interacting quintessence model
Indian Academy of Sciences (India)
Binayak S Choudhury
2018-03-16
Mar 16, 2018 ... Accelerated expansion of the Universe; quintessence; dynamical system; Friedmann–Lemaitre–. Robertson–Walker ... accepted theoretical model. One of the .... Thus, quintessence loses its self-strength and gives dark matter.
Modeling of truck's braking dynamics with ABS
Directory of Open Access Journals (Sweden)
Maxym DYACHUK
2014-09-01
Full Text Available In the article some questions of ABS simulation on the basis of plane vehicle's dynamics and automatic modeling are considered. The author's algorithm of ABS modulators control is presented.
Eggo, Rosalind M; Lenczner, Michael
2015-01-01
Background Multiple waves of transmission during infectious disease epidemics represent a major public health challenge, but the ecological and behavioral drivers of epidemic resurgence are poorly understood. In theory, community structure—aggregation into highly intraconnected and loosely interconnected social groups—within human populations may lead to punctuated outbreaks as diseases progress from one community to the next. However, this explanation has been largely overlooked in favor of temporal shifts in environmental conditions and human behavior and because of the difficulties associated with estimating large-scale contact patterns. Objective The aim was to characterize naturally arising patterns of human contact that are capable of producing simulated epidemics with multiple wave structures. Methods We used an extensive dataset of proximal physical contacts between users of a public Wi-Fi Internet system to evaluate the epidemiological implications of an empirical urban contact network. We characterized the modularity (community structure) of the network and then estimated epidemic dynamics under a percolation-based model of infectious disease spread on the network. We classified simulated epidemics as multiwave using a novel metric and we identified network structures that were critical to the network’s ability to produce multiwave epidemics. Results We identified robust community structure in a large, empirical urban contact network from which multiwave epidemics may emerge naturally. This pattern was fueled by a special kind of insularity in which locally popular individuals were not the ones forging contacts with more distant social groups. Conclusions Our results suggest that ordinary contact patterns can produce multiwave epidemics at the scale of a single urban area without the temporal shifts that are usually assumed to be responsible. Understanding the role of community structure in epidemic dynamics allows officials to anticipate epidemic
Energy Technology Data Exchange (ETDEWEB)
Lu, Ping
2014-10-01
Controlling metallic nanoparticle (NP) interactions plays a vital role in the development of new joining techniques (nanosolder) that bond at lower processing temperatures but remain viable at higher temperatures. The pr imary objective of this project is t o develop a fundamental understanding of the actual reaction processes, associated atomic mechanisms, and the resulting microstructure that occur during thermally - driven bond formation concerning metal - metal nano - scale (%3C50nm) interfaces. In this LDRD pr oject, we have studied metallic NPs interaction at the elevated temperatures by combining in - situ transmission electron microscopy (TEM ) using an aberration - corrected scanning transmission electron microscope (AC - STEM) and atomic - scale modeling such as m olecular dynamic (MD) simulations. Various metallic NPs such as Ag, Cu and Au are synthesized by chemical routines. Numerous in - situ e xperiments were carried out with focus of the research on study of Ag - Cu system. For the first time, using in - situ STEM he ating experiments , we directly observed t he formation of a 3 - dimensional (3 - D) epitaxial Cu - Ag core - shell nanoparticle during the thermal interaction of Cu and Ag NPs at elevated temperatures (150 - 300 o C). The reaction takes place at temperatures as low as 150 o C and was only observed when care was taken to circumvent the effects of electron beam irradiation during STEM imaging. Atomic - scale modeling verified that the Cu - Ag core - shell structure is energetically favored, and indicated that this phenomenon is a nano - scale effect related to the large surface - to - volume ratio of the NPs. The observation potentially can be used for developing new nanosolder technology that uses Ag shell as the "glue" that stic ks the particles of Cu together. The LDRD has led to several journal publications and numerous conference presentations, and a TA. In addition, we have developed new TEM characterization techniques and phase
Dynamic Models of Insurgent Activity
2014-05-19
one dimension that has recently been studied in the computer science community. The model involves movement with a speed proportional to a “fear...more realistic model of human locomotion. The movement of the criminal agents follows a biased Levy flight with step sizes distributed according to a...power-law distribution. The biased Brownian motion of the original model is then derived as a special case. Starting with an agent-based model, we
Dennis, Ann M.; Herbeck, Joshua T.; Brown, Andrew Leigh; Kellam, Paul; de Oliveira, Tulio; Pillay, Deenan; Fraser, Christophe; Cohen, Myron S.
2014-01-01
Efficient and effective HIV prevention measures for generalized epidemics in sub-Saharan Africa have not yet been validated at the population-level. Design and impact evaluation of such measures requires fine-scale understanding of local HIV transmission dynamics. The novel tools of HIV phylogenetics and molecular epidemiology may elucidate these transmission dynamics. Such methods have been incorporated into studies of concentrated HIV epidemics to identify proximate and determinant traits associated with ongoing transmission. However, applying similar phylogenetic analyses to generalized epidemics, including the design and evaluation of prevention trials, presents additional challenges. Here we review the scope of these methods and present examples of their use in concentrated epidemics in the context of prevention. Next, we describe the current uses for phylogenetics in generalized epidemics, and discuss their promise for elucidating transmission patterns and informing prevention trials. Finally, we review logistic and technical challenges inherent to large-scale molecular epidemiological studies of generalized epidemics, and suggest potential solutions. PMID:24977473
Quantum dynamics modeled by interacting trajectories
Cruz-Rodríguez, L.; Uranga-Piña, L.; Martínez-Mesa, A.; Meier, C.
2018-03-01
We present quantum dynamical simulations based on the propagation of interacting trajectories where the effect of the quantum potential is mimicked by effective pseudo-particle interactions. The method is applied to several quantum systems, both for bound and scattering problems. For the bound systems, the quantum ground state density and zero point energy are shown to be perfectly obtained by the interacting trajectories. In the case of time-dependent quantum scattering, the Eckart barrier and uphill ramp are considered, with transmission coefficients in very good agreement with standard quantum calculations. Finally, we show that via wave function synthesis along the trajectories, correlation functions and energy spectra can be obtained based on the dynamics of interacting trajectories.
Stochastic population dynamic models as probability networks
M.E. and D.C. Lee. Borsuk
2009-01-01
The dynamics of a population and its response to environmental change depend on the balance of birth, death and age-at-maturity, and there have been many attempts to mathematically model populations based on these characteristics. Historically, most of these models were deterministic, meaning that the results were strictly determined by the equations of the model and...
Morin, Cory; Monaghan, Andrew; Quattrochi, Dale; Crosson, William; Hayden, Mary; Ernst, Kacey
2015-01-01
Dengue fever is a mosquito-borne viral disease reemerging throughout much of the tropical Americas. Dengue virus transmission is explicitly influenced by climate and the environment through its primary vector, Aedes aegypti. Temperature regulates Ae. aegypti development, survival, and replication rates as well as the incubation period of the virus within the mosquito. Precipitation provides water for many of the preferred breeding habitats of the mosquito, including buckets, old tires, and other places water can collect. Although transmission regularly occurs along the border region in Mexico, dengue virus transmission in bordering Arizona has not occurred. Using NASA's TRMM (Tropical Rainfall Measuring Mission) satellite for precipitation input and Daymet for temperature and supplemental precipitation input, we modeled dengue transmission along a US-Mexico transect using a dynamic dengue transmission model that includes interacting vector ecology and epidemiological components. Model runs were performed for 5 cities in Sonora, Mexico and southern Arizona. Employing a Monte Carlo approach, we performed ensembles of several thousands of model simulations in order to resolve the model uncertainty arising from using different combinations of parameter values that are not well known. For cities with reported dengue case data, the top model simulations that best reproduced dengue case numbers were retained and their parameter values were extracted for comparison. These parameter values were used to run simulations in areas where dengue virus transmission does not occur or where dengue fever case data was unavailable. Additional model runs were performed to reveal how changes in climate or parameter values could alter transmission risk along the transect. The relative influence of climate variability and model parameters on dengue virus transmission is assessed to help public health workers prepare location specific infection prevention strategies.
Bond graph modeling of nuclear reactor dynamics
International Nuclear Information System (INIS)
Tylee, J.L.
1981-01-01
A tenth-order linear model of a pressurized water reactor (PWR) is developed using bond graph techniques. The model describes the nuclear heat generation process and the transfer of this heat to the reactor coolant. Comparisons between the calculated model response and test data from a small-scale PWR show the model to be an adequate representation of the actual plant dynamics. Possible application of the model in an advanced plant diagnostic system is discussed
Swarm Intelligence for Urban Dynamics Modelling
International Nuclear Information System (INIS)
Ghnemat, Rawan; Bertelle, Cyrille; Duchamp, Gerard H. E.
2009-01-01
In this paper, we propose swarm intelligence algorithms to deal with dynamical and spatial organization emergence. The goal is to model and simulate the developement of spatial centers using multi-criteria. We combine a decentralized approach based on emergent clustering mixed with spatial constraints or attractions. We propose an extension of the ant nest building algorithm with multi-center and adaptive process. Typically, this model is suitable to analyse and simulate urban dynamics like gentrification or the dynamics of the cultural equipment in urban area.
Swarm Intelligence for Urban Dynamics Modelling
Ghnemat, Rawan; Bertelle, Cyrille; Duchamp, Gérard H. E.
2009-04-01
In this paper, we propose swarm intelligence algorithms to deal with dynamical and spatial organization emergence. The goal is to model and simulate the developement of spatial centers using multi-criteria. We combine a decentralized approach based on emergent clustering mixed with spatial constraints or attractions. We propose an extension of the ant nest building algorithm with multi-center and adaptive process. Typically, this model is suitable to analyse and simulate urban dynamics like gentrification or the dynamics of the cultural equipment in urban area.
Understanding and Modeling Teams As Dynamical Systems
Gorman, Jamie C.; Dunbar, Terri A.; Grimm, David; Gipson, Christina L.
2017-01-01
By its very nature, much of teamwork is distributed across, and not stored within, interdependent people working toward a common goal. In this light, we advocate a systems perspective on teamwork that is based on general coordination principles that are not limited to cognitive, motor, and physiological levels of explanation within the individual. In this article, we present a framework for understanding and modeling teams as dynamical systems and review our empirical findings on teams as dynamical systems. We proceed by (a) considering the question of why study teams as dynamical systems, (b) considering the meaning of dynamical systems concepts (attractors; perturbation; synchronization; fractals) in the context of teams, (c) describe empirical studies of team coordination dynamics at the perceptual-motor, cognitive-behavioral, and cognitive-neurophysiological levels of analysis, and (d) consider the theoretical and practical implications of this approach, including new kinds of explanations of human performance and real-time analysis and performance modeling. Throughout our discussion of the topics we consider how to describe teamwork using equations and/or modeling techniques that describe the dynamics. Finally, we consider what dynamical equations and models do and do not tell us about human performance in teams and suggest future research directions in this area. PMID:28744231
Modeling HIV transmission and AIDS in the united states
Hethcote, Herbert W
1992-01-01
The disease that came to be called acquired immunodeficiency syndrome (AIDS) was first identified in the summer of 1981. By that time, nearly 100,000 persons in the United States may have been infected with human immunodeficiency virus (HIV). By the time the routes of transmission were clearly identified and HIV was established as the cause of AIDS in 1983, over 300,000 people may have been infected. That number has continued to increase, with approximately 1,000,000 Americans believed to be infected in 1991. The epidemic is of great public health concern because HlV is infectious, causes severe morbidity and death in most if not all of those infected, and often occurs in relatively young persons. In addition, the cost of medical care for a person with HIV disease is high, and the medical care needs of HIV-infected persons place a severe burden on the medical care systems in many areas. Understanding and controlling the HIV epidemic is a particularly difficult challenge. The long and variable period between H...
Directory of Open Access Journals (Sweden)
M Wolkewitz
2008-01-01
Full Text Available Background In addition to the close contact between patients and medical staff, the contamination of surfaces plays an important role in the transmission of pathogens such as vancomycin-resistant enterococci (VRE. Mathematical modeling is a very convenient tool for hospital infection control as it allows the quantitative prediction of the effects of special hygiene and control interventions. Methods We present a compartmental model which describes the dynamics of transmission from patient to patient, also taking into account the interaction with medical staff and environmental contamination. Empirical data from a VRE outbreak in the onco-haematological unit at the University Medical Center Freiburg (Germany were collected with 100 consecutive admissions being followed up for 90 days. Stochastical simulations were used to predict the prevalence of patients colonised with VRE at the time when at least one of the following interventions were introduced: hand hygiene, disinfection of surfaces, cohorting, screening and antibiotic reduction. Results Graphical figures show the temporal dynamics of several simulation scenarios. If no prevention or intervention is present, simulations based on transmission models predict an expected endemic prevalence per ward of 0.83 (95% CI:0.66, 1.00 after the first infected person enters the unit. Interventions may reduce this prevalence, but only the combination of several interventions can control a VRE outbreak. Conclusions The model predicts that only the combination of several interventions can control an VRE outbreak in this setting. The inclusion of environmental contamination improves the compartmental model and allows a prediction of the efficacy of the disinfection of surfaces. These results can be applied to other settings and will therefore help to understand and control the spread of nosocomial pathogens.
Directory of Open Access Journals (Sweden)
Pak Kin Wong
2015-01-01
Full Text Available A novel dual-belt Van Doorne’s continuous variable transmission (DBVCVT system, which is applicable to heavy-duty vehicles, has been previously proposed by the authors in order to improve the low torque capacity of traditional single-belt CVT. This DBVCVT is a novel design among continuously variable transmissions and is necessary to be prototyped for experimental study, and the analytical dynamic model for this DBVCVT also needs to be experimentally validated. So, this work originally fabricated a prototype of DBVCVT and integrates this prototype to a light-load hardware-in-the-loop test rig by replacing the engine and load equipment with the AC motor and magnetic powder dynamometer. Moreover, with the use of this newly developed test rig, this work implements the experimental study of this DBVCVT for the first time. The comparison of experimental and simulation results validates the previously proposed analytical model for DBVCVT, and some basic characteristics of the DBVCVT in terms of the reliability, speed ratio, and transmission efficiency are also experimentally studied. In all, this developed test rig with the analytical model lays the foundation for further study on this novel DBVCVT.
Energy Technology Data Exchange (ETDEWEB)
Gross, Volker [ZF Friedrichshafen AG, Friedrichshafen (Germany)
2011-07-01
The legal regulations and the customers' requirements as regards vehicle comfort are growing more and more stringent. This also includes the transmission systems, as they are expected not so show any obvious acoustic or dynamic weaknesses. Modern simulation methods permit evaluation and optimization of structure-borne and airborne noise in the early stage of development. Especially the FE method is a well-established technique for the simulation of structure-borne sound. With regard to complex transmissions, multibody simulations (MBS) can provide valuable insights for a realistic evaluation of the dynamic behaviour of a transmission. This is demonstrated using a truck transmission as an example. (orig.)
Optical modeling of fiber organic photovoltaic structures using a transmission line method.
Moshonas, N; Stathopoulos, N A; O'Connor, B T; Bedeloglu, A Celik; Savaidis, S P; Vasiliadis, S
2017-12-01
An optical model has been developed and evaluated for the calculation of the external quantum efficiency of cylindrical fiber photovoltaic structures. The model is based on the transmission line theory and has been applied on single and bulk heterojunction fiber-photovoltaic cells. Using this model, optimum design characteristics have been proposed for both configurations, and comparison with experimental results has been assessed.
Dynamical models of spiral galaxies
International Nuclear Information System (INIS)
Grosbol, P.
1990-01-01
The effects of changing the basic parameters of rotation curve steepness, amount of bulge, and pitch angle of the imposed spiral pattern in the galactic model of Contoupolos and Grosbel (1986) are investigated. The general conclusions of the model are confirmed and shown to be insensitive to the specific choice of parameters for the galactic potential. The exact amplitude at which the nonlinear effects at the 4:1 resonance become important do, however, depend on the model
Energy Balance Models and Planetary Dynamics
Domagal-Goldman, Shawn
2012-01-01
We know that planetary dynamics can have a significant affect on the climate of planets. Planetary dynamics dominate the glacial-interglacial periods on Earth, leaving a significant imprint on the geological record. They have also been demonstrated to have a driving influence on the climates of other planets in our solar system. We should therefore expect th.ere to be similar relationships on extrasolar planets. Here we describe a simple energy balance model that can predict the growth and thickness of glaciers, and their feedbacks on climate. We will also describe model changes that we have made to include planetary dynamics effects. This is the model we will use at the start of our collaboration to handle the influence of dynamics on climate.
Stirling Engine Dynamic System Modeling
Nakis, Christopher G.
2004-01-01
The Thermo-Mechanical systems branch at the Glenn Research Center focuses a large amount time on Stirling engines. These engines will be used on missions where solar power is inefficient, especially in deep space. I work with Tim Regan and Ed Lewandowski who are currently developing and validating a mathematical model for the Stirling engines. This model incorporates all aspects of the system including, mechanical, electrical and thermodynamic components. Modeling is done through Simplorer, a program capable of running simulations of the model. Once created and then proven to be accurate, a model is used for developing new ideas for engine design. My largest specific project involves varying key parameters in the model and quantifying the results. This can all be done relatively trouble-free with the help of Simplorer. Once the model is complete, Simplorer will do all the necessary calculations. The more complicated part of this project is determining which parameters to vary. Finding key parameters depends on the potential for a value to be independently altered in the design. For example, a change in one dimension may lead to a proportional change to the rest of the model, and no real progress is made. Also, the ability for a changed value to have a substantial impact on the outputs of the system is important. Results will be condensed into graphs and tables with the purpose of better communication and understanding of the data. With the changing of these parameters, a more optimal design can be created without having to purchase or build any models. Also, hours and hours of results can be simulated in minutes. In the long run, using mathematical models can save time and money. Along with this project, I have many other smaller assignments throughout the summer. My main goal is to assist in the processes of model development, validation and testing.
Transmission-line-circuit model of an 85-TW, 25-MA pulsed-power accelerator
B. T. Hutsel; P. A. Corcoran; M. E. Cuneo; M. R. Gomez; M. H. Hess; D. D. Hinshelwood; C. A. Jennings; G. R. Laity; D. C. Lamppa; R. D. McBride; J. K. Moore; A. Myers; D. V. Rose; S. A. Slutz; W. A. Stygar
2018-01-01
We have developed a physics-based transmission-line-circuit model of the Z pulsed-power accelerator. The 33-m-diameter Z machine generates a peak electrical power as high as 85 TW, and delivers as much as 25 MA to a physics load. The circuit model is used to design and analyze experiments conducted on Z. The model consists of 36 networks of transmission-line-circuit elements and resistors that represent each of Zs 36 modules. The model of each module includes a Marx generator, intermediate-en...
Tam, Kim-Pong; Lee, Sau-Lai; Kim, Young-Hoon; Li, Yanmei; Chao, Melody Manchi
2012-08-01
What values do parents want to transmit to children? The intersubjective model of value transmission posits that parents want to transmit not only the values they personally endorse but also the values they perceive to be normatively important in the society. The present research shows support to this premise. Furthermore, Studies 1 and 2 revealed that the use of perceived norms is moderated by families' social contexts and parents' personality: It was particularly pronounced among parents who were immigrants, who had a stronger need for closure, and who were more conforming. In addition, Studies 3 and 4 demonstrated that parents' perceived norms can explain actual value transmission: Values parents perceived to be normatively important were to some extent internalized by children. The intersubjective model paves some new directions for value transmission research, contributes to the understanding of cultural transmission and cultural change, and extends the intersubjective approach to culture.
Brand Equity Evolution: a System Dynamics Model
Directory of Open Access Journals (Sweden)
Edson Crescitelli
2009-04-01
Full Text Available One of the greatest challenges in brand management lies in monitoring brand equity over time. This paper aimsto present a simulation model able to represent this evolution. The model was drawn on brand equity concepts developed by Aaker and Joachimsthaler (2000, using the system dynamics methodology. The use ofcomputational dynamic models aims to create new sources of information able to sensitize academics and managers alike to the dynamic implications of their brand management. As a result, an easily implementable model was generated, capable of executing continuous scenario simulations by surveying casual relations among the variables that explain brand equity. Moreover, the existence of a number of system modeling tools will allow extensive application of the concepts used in this study in practical situations, both in professional and educational settings
Discrete dynamic modeling of cellular signaling networks.
Albert, Réka; Wang, Rui-Sheng
2009-01-01
Understanding signal transduction in cellular systems is a central issue in systems biology. Numerous experiments from different laboratories generate an abundance of individual components and causal interactions mediating environmental and developmental signals. However, for many signal transduction systems there is insufficient information on the overall structure and the molecular mechanisms involved in the signaling network. Moreover, lack of kinetic and temporal information makes it difficult to construct quantitative models of signal transduction pathways. Discrete dynamic modeling, combined with network analysis, provides an effective way to integrate fragmentary knowledge of regulatory interactions into a predictive mathematical model which is able to describe the time evolution of the system without the requirement for kinetic parameters. This chapter introduces the fundamental concepts of discrete dynamic modeling, particularly focusing on Boolean dynamic models. We describe this method step-by-step in the context of cellular signaling networks. Several variants of Boolean dynamic models including threshold Boolean networks and piecewise linear systems are also covered, followed by two examples of successful application of discrete dynamic modeling in cell biology.
Directory of Open Access Journals (Sweden)
Hyun M Yang
2001-06-01
Full Text Available OBJECTIVE: Sensitivity analysis was applied to a mathematical model describing malaria transmission relating global warming and local socioeconomic conditions. METHODS: A previous compartment model was proposed to describe the overall transmission of malaria. This model was built up on several parameters and the prevalence of malaria in a community was characterized by the values assigned to them. To assess the control efforts, the model parameters can vary on broad intervals. RESULTS: By performing the sensitivity analysis on equilibrium points, which represent the level of malaria infection in a community, the different possible scenarios are obtained when the parameters are changed. CONCLUSIONS: Depending on malaria risk, the efforts to control its transmission can be guided by a subset of parameters used in the mathematical model.
SimWIND: A geospatial infrastructure model for optimizing wind power generation and transmission
International Nuclear Information System (INIS)
Phillips, Benjamin R.; Middleton, Richard S.
2012-01-01
Wind is a clean, enduring energy resource with the capacity to satisfy 20% or more of U.S. electricity demand. Presently, wind potential is limited by a paucity of electrical transmission lines and/or capacity between promising wind resources and primary load centers. We present the model SimWIND to address this shortfall. SimWIND is an integrated optimization model for the geospatial arrangement and cost minimization of wind-power generation–transmission–delivery infrastructure. Given a set of possible wind-farm sites, the model simultaneously determines (1) where and how much power to generate and (2) where to build new transmission infrastructure and with what capacity in order to minimize the cost for delivering a targeted amount of power to load. Costs and routing of transmission lines consider geographic and social constraints as well as electricity losses. We apply our model to the Electric Reliability Council of Texas (ERCOT) Interconnection, considering scenarios that deliver up to 20 GW of new wind power. We show that SimWIND could potentially reduce ERCOT's projected ∼$5B transmission network upgrade line length and associated costs by 50%. These results suggest that SimWIND's coupled generation–transmission–delivery modeling approach could play a critical role in enhancing planning efforts and reducing costs for wind energy integration. - Highlights: ► Wind power is limited by transmission capacity between resources and demands. ► SimWIND is a coupled generation-transmission-delivery model for wind infrastructure. ► The model minimizes costs considering realistic transmission routing and networking. ► We show that SimWIND could save 50% of $5B costs for expanding the Texas grid. ► Results suggest SimWIND may play a critical role in enhancings wind planning efforts.
Winskill, Peter; Slater, Hannah C; Griffin, Jamie T; Ghani, Azra C; Walker, Patrick G T
2017-11-01
Although significant progress has been made in reducing malaria transmission globally in recent years, a large number of people remain at risk and hence the gains made are fragile. Funding lags well behind amounts needed to protect all those at risk and ongoing contributions from major donors, such as the President's Malaria Initiative (PMI), are vital to maintain progress and pursue further reductions in burden. We use a mathematical modelling approach to estimate the impact of PMI investments to date in reducing malaria burden and to explore the potential negative impact on malaria burden should a proposed 44% reduction in PMI funding occur. We combined an established mathematical model of Plasmodium falciparum transmission dynamics with epidemiological, intervention, and PMI-financing data to estimate the contribution PMI has made to malaria control via funding for long-lasting insecticide treated nets (LLINs), indoor residual spraying (IRS), and artemisinin combination therapies (ACTs). We estimate that PMI has prevented 185 million (95% CrI: 138 million, 230 million) malaria cases and saved 940,049 (95% CrI: 545,228, 1.4 million) lives since 2005. If funding is maintained, PMI-funded interventions are estimated to avert a further 162 million (95% CrI: 116 million, 194 million) cases, saving a further 692,589 (95% CrI: 392,694, 955,653) lives between 2017 and 2020. With an estimate of US$94 (95% CrI: US$51, US$166) per Disability Adjusted Life Year (DALY) averted, PMI-funded interventions are highly cost-effective. We also demonstrate the further impact of this investment by reducing caseloads on health systems. If a 44% reduction in PMI funding were to occur, we predict that this loss of direct aid could result in an additional 67 million (95% CrI: 49 million, 82 million) cases and 290,649 (95% CrI: 167,208, 395,263) deaths between 2017 and 2020. We have not modelled indirect impacts of PMI funding (such as health systems strengthening) in this analysis. Our
Directory of Open Access Journals (Sweden)
Peter Winskill
2017-11-01
Full Text Available Although significant progress has been made in reducing malaria transmission globally in recent years, a large number of people remain at risk and hence the gains made are fragile. Funding lags well behind amounts needed to protect all those at risk and ongoing contributions from major donors, such as the President's Malaria Initiative (PMI, are vital to maintain progress and pursue further reductions in burden. We use a mathematical modelling approach to estimate the impact of PMI investments to date in reducing malaria burden and to explore the potential negative impact on malaria burden should a proposed 44% reduction in PMI funding occur.We combined an established mathematical model of Plasmodium falciparum transmission dynamics with epidemiological, intervention, and PMI-financing data to estimate the contribution PMI has made to malaria control via funding for long-lasting insecticide treated nets (LLINs, indoor residual spraying (IRS, and artemisinin combination therapies (ACTs. We estimate that PMI has prevented 185 million (95% CrI: 138 million, 230 million malaria cases and saved 940,049 (95% CrI: 545,228, 1.4 million lives since 2005. If funding is maintained, PMI-funded interventions are estimated to avert a further 162 million (95% CrI: 116 million, 194 million cases, saving a further 692,589 (95% CrI: 392,694, 955,653 lives between 2017 and 2020. With an estimate of US$94 (95% CrI: US$51, US$166 per Disability Adjusted Life Year (DALY averted, PMI-funded interventions are highly cost-effective. We also demonstrate the further impact of this investment by reducing caseloads on health systems. If a 44% reduction in PMI funding were to occur, we predict that this loss of direct aid could result in an additional 67 million (95% CrI: 49 million, 82 million cases and 290,649 (95% CrI: 167,208, 395,263 deaths between 2017 and 2020. We have not modelled indirect impacts of PMI funding (such as health systems strengthening in this analysis
Dynamic Modelling with "MLE-Energy Dynamic" for Primary School
Giliberti, Enrico; Corni, Federico
During the recent years simulation and modelling are growing instances in science education. In primary school, however, the main use of software is the simulation, due to the lack of modelling software tools specially designed to fit/accomplish the needs of primary education. In particular primary school teachers need to use simulation in a framework that is both consistent and simple enough to be understandable by children [2]. One of the possible area to approach modelling is about the construction of the concept of energy, in particular for what concerns the relations among substance, potential, power [3]. Following the previous initial research results with this approach [2], and with the static version of the software MLE Energy [1], we suggest the design and the experimentation of a dynamic modelling software—MLE dynamic-capable to represent dynamically the relations occurring when two substance-like quantities exchange energy, modifying their potential. By means of this software the user can graphically choose the dependent and independent variables and leave the other parameters fixed. The software has been initially evaluated, during a course of science education with a group of primary school teachers-to-be, to test the ability of the software to improve teachers' way of thinking in terms of substance-like quantities and their effects (graphical representation of the extensive, intensive variables and their mutual relations); moreover, the software has been tested with a group of primary school teachers, asking their opinion about the software didactical relevance in the class work.
Computer models for fading channels with applications to digital transmission
Loo, Chun; Secord, Norman
1991-11-01
The authors describe computer models for Rayleigh, Rician, log-normal, and land-mobile-satellite fading channels. All computer models for the fading channels are based on the manipulation of a white Gaussian random process. This process is approximated by a sum of sinusoids with random phase angle. These models compare very well with analytical models in terms of their probability distribution of envelope and phase of the fading signal. For the land mobile satellite fading channel, results of level crossing rate and average fade duration are given. These results show that the computer models can provide a good coarse estimate of the time statistic of the faded signal. Also, for the land-mobile-satellite fading channel, the results show that a 3-pole Butterworth shaping filter should be used with the model. An example of the application of the land-mobile-satellite fading-channel model to predict the performance of a differential phase-shift keying signal is described.
DEFF Research Database (Denmark)
Christensen, Claus Lynge; Rindel, Jens Holger
2006-01-01
The paper describes a new method for simulating the frequency-dependent reflection and transmission of reflector arrays, and the frequency-dependent airborne sound insulation between rooms by means of a room acoustic computer model. The method makes use of a transparency method in the ray...... of the partition, and this is useful for the auralization of sound transmission through different building constructions. The acoustic properties like volume, reverberation time, and the area of the transmitting surfaces are included in the simulation....
Optimal treatment interruptions control of TB transmission model
Nainggolan, Jonner; Suparwati, Titik; Kawuwung, Westy B.
2018-03-01
A tuberculosis model which incorporates treatment interruptions of infectives is established. Optimal control of individuals infected with active TB is given in the model. It is obtained that the control reproduction numbers is smaller than the reproduction number, this means treatment controls could optimize the decrease in the spread of active TB. For this model, controls on treatment of infection individuals to reduce the actively infected individual populations, by application the Pontryagins Maximum Principle for optimal control. The result further emphasized the importance of controlling disease relapse in reducing the number of actively infected and treatment interruptions individuals with tuberculosis.
Directory of Open Access Journals (Sweden)
Pierre Nouvellet
2013-11-01
Full Text Available Chagas disease has a major impact on human health in Latin America and is becoming of global concern due to international migrations. Trypanosoma cruzi, the etiological agent of the disease, is one of the rare human parasites transmitted by the feces of its vector, as it is unable to reach the salivary gland of the insect. This stercorarian transmission is notoriously poorly understood, despite its crucial role in the ecology and evolution of the pathogen and the disease. The objective of this study was to quantify the probability of T. cruzi vectorial transmission to humans, and to use such an estimate to predict human prevalence from entomological data. We developed several models of T. cruzi transmission to estimate the probability of transmission from vector to host. Using datasets from the literature, we estimated the probability of transmission per contact with an infected triatomine to be 5.8 × 10(-4 (95%CI: [2.6 ; 11.0] × 10(-4. This estimate was consistent across triatomine species, robust to variations in other parameters, and corresponded to 900-4,000 contacts per case. Our models subsequently allowed predicting human prevalence from vector abundance and infection rate in 7/10 independent datasets covering various triatomine species and epidemiological situations. This low probability of T. cruzi transmission reflected well the complex and unlikely mechanism of transmission via insect feces, and allowed predicting human prevalence from basic entomological data. Although a proof of principle study would now be valuable to validate our models' predictive ability in an even broader range of entomological and ecological settings, our quantitative estimate could allow switching the evaluation of disease risk and vector control program from purely entomological indexes to parasitological measures, as commonly done for other major vector borne diseases. This might lead to different quantitative perspectives as these indexes are well known
Dynamics of a Fractional Order HIV Infection Model with Specific Functional Response and Cure Rate
Directory of Open Access Journals (Sweden)
Adnane Boukhouima
2017-01-01
Full Text Available We propose a fractional order model in this paper to describe the dynamics of human immunodeficiency virus (HIV infection. In the model, the infection transmission process is modeled by a specific functional response. First, we show that the model is mathematically and biologically well posed. Second, the local and global stabilities of the equilibria are investigated. Finally, some numerical simulations are presented in order to illustrate our theoretical results.
A Comparison of Dynamics in Two Models for the Spread of a Vector-Borne Disease
DEFF Research Database (Denmark)
Græsbøll, Kaare; Sumner, T.; Enøe, Claes
2016-01-01
In 2007, bluetongue virus (BTV) was introduced to both Denmark (DK) and the United Kingdom (UK). For this reason, simulation models were built to predict scenarios for future incursions. The DK and UK models have a common description of within-herd dynamics, but differ greatly in their descriptio...... sensitivity to the level of vaccine uptake and has lower variability compared with a kernel-based model. However, a model using a transmission kernel requires less detailed data and is often faster....
armax, oe and ssif model predictors for power transmission
African Journals Online (AJOL)
Vincent
collected for thirteen different parameters that influences the evaluation and analysis in the case study area. ... regression model for short term load prediction while Haida and Muto ...... The OE is a special stochastic case which is achieved by.
CRLH Transmission Lines for Telecommunications: Fast and Effective Modeling
Directory of Open Access Journals (Sweden)
Juanjuan Gao
2017-01-01
Full Text Available A different parameter extraction approach based on zero immittances for composite right/left-handed (CRLH structure is presented. For lossless unit cell equivalent circuit model, LC parameters of series and parallel branches are extracted according to series resonance frequency and parallel resonance frequency, respectively. This approach can be applied to symmetric and unbalanced CRLH structures. The parameter extraction procedure is provided and validated by T-type unit cell model. The responses of distributed prototype and extracted equivalent LC circuit model are in good agreement. The equivalent circuit modeling can improve the degree of freedom in the CRLH TLs design. This parameter extraction method provides an effective and straightforward way in CRLH metamaterials design and applications in telecommunication systems.
Modelling the physics in iterative reconstruction for transmission computed tomography
Nuyts, Johan; De Man, Bruno; Fessler, Jeffrey A.; Zbijewski, Wojciech; Beekman, Freek J.
2013-01-01
There is an increasing interest in iterative reconstruction (IR) as a key tool to improve quality and increase applicability of X-ray CT imaging. IR has the ability to significantly reduce patient dose, it provides the flexibility to reconstruct images from arbitrary X-ray system geometries and it allows to include detailed models of photon transport and detection physics, to accurately correct for a wide variety of image degrading effects. This paper reviews discretisation issues and modelling of finite spatial resolution, Compton scatter in the scanned object, data noise and the energy spectrum. Widespread implementation of IR with highly accurate model-based correction, however, still requires significant effort. In addition, new hardware will provide new opportunities and challenges to improve CT with new modelling. PMID:23739261
Grid Transmission Expansion Planning Model Based on Grid Vulnerability
Tang, Quan; Wang, Xi; Li, Ting; Zhang, Quanming; Zhang, Hongli; Li, Huaqiang
2018-03-01
Based on grid vulnerability and uniformity theory, proposed global network structure and state vulnerability factor model used to measure different grid models. established a multi-objective power grid planning model which considering the global power network vulnerability, economy and grid security constraint. Using improved chaos crossover and mutation genetic algorithm to optimize the optimal plan. For the problem of multi-objective optimization, dimension is not uniform, the weight is not easy given. Using principal component analysis (PCA) method to comprehensive assessment of the population every generation, make the results more objective and credible assessment. the feasibility and effectiveness of the proposed model are validated by simulation results of Garver-6 bus system and Garver-18 bus.
Dynamics of the standard model
Donoghue, John F; Holstein, Barry R
2014-01-01
Describing the fundamental theory of particle physics and its applications, this book provides a detailed account of the Standard Model, focusing on techniques that can produce information about real observed phenomena. The book begins with a pedagogic account of the Standard Model, introducing essential techniques such as effective field theory and path integral methods. It then focuses on the use of the Standard Model in the calculation of physical properties of particles. Rigorous methods are emphasized, but other useful models are also described. This second edition has been updated to include recent theoretical and experimental advances, such as the discovery of the Higgs boson. A new chapter is devoted to the theoretical and experimental understanding of neutrinos, and major advances in CP violation and electroweak physics have been given a modern treatment. This book is valuable to graduate students and researchers in particle physics, nuclear physics and related fields.
Forecasting with Dynamic Regression Models
Pankratz, Alan
2012-01-01
One of the most widely used tools in statistical forecasting, single equation regression models is examined here. A companion to the author's earlier work, Forecasting with Univariate Box-Jenkins Models: Concepts and Cases, the present text pulls together recent time series ideas and gives special attention to possible intertemporal patterns, distributed lag responses of output to input series and the auto correlation patterns of regression disturbance. It also includes six case studies.
Directory of Open Access Journals (Sweden)
Kuusela Jussi
2009-01-01
Full Text Available Abstract Background Recent studies have revealed expansion by an array of Filarioid nematodes' into the northern boreal region of Finland. The vector-borne nematode, Setaria tundra, caused a serious disease outbreak in the Finnish reindeer population in 2003–05. The main aim of this study was to understand the outbreak dynamics and the rapid expansion of S. tundra in the sub arctic. We describe the vectors of S. tundra, and its development in vectors, for the first time. Finally we discuss the results in the context of the host-parasite ecology of S. tundra in Finland Results Development of S. tundra to the infective stage occurs in mosquitoes, (genera Aedes and Anopheles. We consider Aedes spp. the most important vectors. The prevalence of S. tundra naturally infected mosquitoes from Finland varied from 0.5 to 2.5%. The rate of development in mosquitoes was temperature-dependent. Infective larvae were present approximately 14 days after a blood meal in mosquitoes maintained at room temperature (mean 21 C, but did not develop in mosquitoes maintained outside for 22 days at a mean temperature of 14.1 C. The third-stage (infective larvae were elongated (mean length 1411 μm (SD 207, and width 28 μm (SD 2. The anterior end was blunt, and bore two liplike structures, the posterior end slight tapering with a prominent terminal papilla. Infective larvae were distributed anteriorly in the insect's body, the highest abundance being 70 larvae in one mosquito. A questionnaire survey revealed that the peak activity of Culicidae in the reindeer herding areas of Finland was from the middle of June to the end of July and that warm summer weather was associated with reindeer flocking behaviour on mosquito-rich wetlands. Conclusion In the present work, S. tundra vectors and larval development were identified and described for the first time. Aedes spp. mosquitoes likely serve as the most important and competent vectors for S. tundra in Finland. Warm summers
Dynamic Modelling Of A SCARA Robot
Turiel, J. Perez; Calleja, R. Grossi; Diez, V. Gutierrez
1987-10-01
This paper describes a method for modelling industrial robots that considers dynamic approach to manipulation systems motion generation, obtaining the complete dynamic model for the mechanic part of the robot and taking into account the dynamic effect of actuators acting at the joints. For a four degree of freedom SCARA robot we obtain the dynamic model for the basic (minimal) configuration, that is, the three degrees of freedom that allow us to place the robot end effector in a desired point, using the Lagrange Method to obtain the dynamic equations in matrix form. The manipulator is considered to be a set of rigid bodies inter-connected by joints in the form of simple kinematic pairs. Then, the state space model is obtained for the actuators that move the robot joints, uniting the models of the single actuators, that is, two DC permanent magnet servomotors and an electrohydraulic actuator. Finally, using a computer simulation program written in FORTRAN language, we can compute the matrices of the complete model.
Dynamic modeling of IGCC power plants
International Nuclear Information System (INIS)
Casella, F.; Colonna, P.
2012-01-01
Integrated Gasification Combined Cycle (IGCC) power plants are an effective option to reduce emissions and implement carbon-dioxide sequestration. The combination of a very complex fuel-processing plant and a combined cycle power station leads to challenging problems as far as dynamic operation is concerned. Dynamic performance is extremely relevant because recent developments in the electricity market push toward an ever more flexible and varying operation of power plants. A dynamic model of the entire system and models of its sub-systems are indispensable tools in order to perform computer simulations aimed at process and control design. This paper presents the development of the lumped-parameters dynamic model of an entrained-flow gasifier, with special emphasis on the modeling approach. The model is implemented into software by means of the Modelica language and validated by comparison with one set of data related to the steady operation of the gasifier of the Buggenum power station in the Netherlands. Furthermore, in order to demonstrate the potential of the proposed modeling approach and the use of simulation for control design purposes, a complete model of an exemplary IGCC power plant, including its control system, has been developed, by re-using existing models of combined cycle plant components; the results of a load dispatch ramp simulation are presented and shortly discussed. - Highlights: ► The acausal dynamic model of an entrained gasifier has been developed. ► The model can be used to perform system optimization and control studies. ► The model has been validated using field data. ► Model use is illustrated with an example showing the transient of an IGCC plant.
Automated adaptive inference of phenomenological dynamical models
Daniels, Bryan
Understanding the dynamics of biochemical systems can seem impossibly complicated at the microscopic level: detailed properties of every molecular species, including those that have not yet been discovered, could be important for producing macroscopic behavior. The profusion of data in this area has raised the hope that microscopic dynamics might be recovered in an automated search over possible models, yet the combinatorial growth of this space has limited these techniques to systems that contain only a few interacting species. We take a different approach inspired by coarse-grained, phenomenological models in physics. Akin to a Taylor series producing Hooke's Law, forgoing microscopic accuracy allows us to constrain the search over dynamical models to a single dimension. This makes it feasible to infer dynamics with very limited data, including cases in which important dynamical variables are unobserved. We name our method Sir Isaac after its ability to infer the dynamical structure of the law of gravitation given simulated planetary motion data. Applying the method to output from a microscopically complicated but macroscopically simple biological signaling model, it is able to adapt the level of detail to the amount of available data. Finally, using nematode behavioral time series data, the method discovers an effective switch between behavioral attractors after the application of a painful stimulus.
An SIS model for cultural trait transmission with conformity bias.
Walters, Caroline E; Kendal, Jeremy R
2013-12-01
Epidemiological models have been applied to human health-related behaviors that are affected by social interaction. Typically these models have not considered conformity bias, that is, the exaggerated propensity to adopt commonly observed behaviors or opinions, or content biases, where the content of the learned trait affects the probability of adoption. Here we consider an interaction of these two effects, presenting an SIS-type model for the spread and persistence of a behavior which is transmitted via social learning. Uptake is controlled by a nonlinear dependence on the proportion of individuals demonstrating the behavior in a population. Three equilibrium solutions are found, their linear stability is analyzed and the results are compared with a model for unbiased social learning. Our analysis focuses on the effects of the strength of conformity bias and the effects of content biases which alter a conformity threshold frequency of the behavior, above which there is an exaggerated propensity for adoption. The strength of the conformity bias is found to qualitatively alter the predictions regarding whether the trait becomes endemic within the population and the proportion of individuals who display the trait when it is endemic. As the conformity strength increases, the number of feasible equilibrium solutions increases from two to three, leading to a situation where the stable equilibrium attained is dependent upon the initial state. Varying the conformity threshold frequency directionally alters the behavior invasion threshold. Finally we discuss the possible application of this model to binge drinking behavior. Copyright © 2013 Elsevier Inc. All rights reserved.
Online Learning of Industrial Manipulators' Dynamics Models
DEFF Research Database (Denmark)
Polydoros, Athanasios
2017-01-01
, it was compared with multiple other state-of-the-art machine learning algorithms. Moreover, the thesis presents the application of the proposed learning method on robot control for achieving trajectory execution while learning the inverse dynamics models on-the-fly . Also it is presented the application...... of the dynamics models. Those mainly derive from physics-based methods and thus they are based on physical properties which are hard to be calculated. In this thesis, is presented, a novel online machine learning approach which is able to model both inverse and forward dynamics models of industrial manipulators....... The proposed method belongs to the class of deep learning and exploits the concepts of self-organization, recurrent neural networks and iterative multivariate Bayesian regression. It has been evaluated on multiple datasets captured from industrial robots while they were performing various tasks. Also...
Dynamic optimization deterministic and stochastic models
Hinderer, Karl; Stieglitz, Michael
2016-01-01
This book explores discrete-time dynamic optimization and provides a detailed introduction to both deterministic and stochastic models. Covering problems with finite and infinite horizon, as well as Markov renewal programs, Bayesian control models and partially observable processes, the book focuses on the precise modelling of applications in a variety of areas, including operations research, computer science, mathematics, statistics, engineering, economics and finance. Dynamic Optimization is a carefully presented textbook which starts with discrete-time deterministic dynamic optimization problems, providing readers with the tools for sequential decision-making, before proceeding to the more complicated stochastic models. The authors present complete and simple proofs and illustrate the main results with numerous examples and exercises (without solutions). With relevant material covered in four appendices, this book is completely self-contained.
Dynamic modeling of the INAPRO aquaponic system
Karimanzira, Divas; Keesman, Karel J.; Kloas, Werner; Baganz, Daniela; Rauschenbach, Thomas
2016-01-01
The use of modeling techniques to analyze aquaponics systems is demonstrated with an example of dynamic modeling for the production of Nile tilapia (Oreochromis niloticus) and tomatoes (Solanum lycopersicon) using the innovative double recirculating aquaponic system ASTAF-PRO. For the management
Dynamic spatial panels : models, methods, and inferences
Elhorst, J. Paul
This paper provides a survey of the existing literature on the specification and estimation of dynamic spatial panel data models, a collection of models for spatial panels extended to include one or more of the following variables and/or error terms: a dependent variable lagged in time, a dependent
A Discrete Dynamical Model of Signed Partitions
Directory of Open Access Journals (Sweden)
G. Chiaselotti
2013-01-01
Full Text Available We use a discrete dynamical model with three evolution rules in order to analyze the structure of a partially ordered set of signed integer partitions whose main properties are actually not known. This model is related to the study of some extremal combinatorial sum problems.
Dynamic Factor Models for the Volatility Surface
DEFF Research Database (Denmark)
van der Wel, Michel; Ozturk, Sait R.; Dijk, Dick van
The implied volatility surface is the collection of volatilities implied by option contracts for different strike prices and time-to-maturity. We study factor models to capture the dynamics of this three-dimensional implied volatility surface. Three model types are considered to examine desirable...
Analysis of a Model for Computer Virus Transmission
Directory of Open Access Journals (Sweden)
Peng Qin
2015-01-01
Full Text Available Computer viruses remain a significant threat to computer networks. In this paper, the incorporation of new computers to the network and the removing of old computers from the network are considered. Meanwhile, the computers are equipped with antivirus software on the computer network. The computer virus model is established. Through the analysis of the model, disease-free and endemic equilibrium points are calculated. The stability conditions of the equilibria are derived. To illustrate our theoretical analysis, some numerical simulations are also included. The results provide a theoretical basis to control the spread of computer virus.
Emerging Infectious Diseases and Blood Safety: Modeling the Transfusion-Transmission Risk.
Kiely, Philip; Gambhir, Manoj; Cheng, Allen C; McQuilten, Zoe K; Seed, Clive R; Wood, Erica M
2017-07-01
While the transfusion-transmission (TT) risk associated with the major transfusion-relevant viruses such as HIV is now very low, during the last 20 years there has been a growing awareness of the threat to blood safety from emerging infectious diseases, a number of which are known to be, or are potentially, transfusion transmissible. Two published models for estimating the transfusion-transmission risk from EIDs, referred to as the Biggerstaff-Petersen model and the European Upfront Risk Assessment Tool (EUFRAT), respectively, have been applied to several EIDs in outbreak situations. We describe and compare the methodological principles of both models, highlighting their similarities and differences. We also discuss the appropriateness of comparing results from the two models. Quantitating the TT risk of EIDs can inform decisions about risk mitigation strategies and their cost-effectiveness. Finally, we present a qualitative risk assessment for Zika virus (ZIKV), an EID agent that has caused several outbreaks since 2007. In the latest and largest ever outbreak, several probable cases of transfusion-transmission ZIKV have been reported, indicating that it is transfusion-transmissible and therefore a risk to blood safety. We discuss why quantitative modeling the TT risk of ZIKV is currently problematic. Crown Copyright © 2017. Published by Elsevier Inc. All rights reserved.
Dynamical modeling of surface tension
International Nuclear Information System (INIS)
Brackbill, J.U.; Kothe, D.B.
1996-01-01
In a recent review it is said that free-surface flows ''represent some of the difficult remaining challenges in computational fluid dynamics''. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin. This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin are discussed
Session 6: Dynamic Modeling and Systems Analysis
Csank, Jeffrey; Chapman, Jeffryes; May, Ryan
2013-01-01
These presentations cover some of the ongoing work in dynamic modeling and dynamic systems analysis. The first presentation discusses dynamic systems analysis and how to integrate dynamic performance information into the systems analysis. The ability to evaluate the dynamic performance of an engine design may allow tradeoffs between the dynamic performance and operability of a design resulting in a more efficient engine design. The second presentation discusses the Toolbox for Modeling and Analysis of Thermodynamic Systems (T-MATS). T-MATS is a Simulation system with a library containing the basic building blocks that can be used to create dynamic Thermodynamic Systems. Some of the key features include Turbo machinery components, such as turbines, compressors, etc., and basic control system blocks. T-MAT is written in the Matlab-Simulink environment and is open source software. The third presentation focuses on getting additional performance from the engine by allowing the limit regulators only to be active when a limit is danger of being violated. Typical aircraft engine control architecture is based on MINMAX scheme, which is designed to keep engine operating within prescribed mechanical/operational safety limits. Using a conditionally active min-max limit regulator scheme, additional performance can be gained by disabling non-relevant limit regulators
Mesoscale Models of Fluid Dynamics
Boghosian, Bruce M.; Hadjiconstantinou, Nicolas G.
During the last half century, enormous progress has been made in the field of computational materials modeling, to the extent that in many cases computational approaches are used in a predictive fashion. Despite this progress, modeling of general hydrodynamic behavior remains a challenging task. One of the main challenges stems from the fact that hydrodynamics manifests itself over a very wide range of length and time scales. On one end of the spectrum, one finds the fluid's "internal" scale characteristic of its molecular structure (in the absence of quantum effects, which we omit in this chapter). On the other end, the "outer" scale is set by the characteristic sizes of the problem's domain. The resulting scale separation or lack thereof as well as the existence of intermediate scales are key to determining the optimal approach. Successful treatments require a judicious choice of the level of description which is a delicate balancing act between the conflicting requirements of fidelity and manageable computational cost: a coarse description typically requires models for underlying processes occuring at smaller length and time scales; on the other hand, a fine-scale model will incur a significantly larger computational cost.
Modelling biased human trust dynamics
Hoogendoorn, M.; Jaffry, S.W.; Maanen, P.P. van; Treur, J.
2013-01-01
Abstract. Within human trust related behaviour, according to the literature from the domains of Psychology and Social Sciences often non-rational behaviour can be observed. Current trust models that have been developed typically do not incorporate non-rational elements in the trust formation
Dynamic model for a boiling water reactor
International Nuclear Information System (INIS)
Muscettola, M.
1963-07-01
A theoretical formulation is derived for the dynamics of a boiling water reactor of the pressure tube and forced circulation type. Attention is concentrated on neutron kinetics, fuel element heat transfer dynamics, and the primary circuit - that is the boiling channel, riser, steam drum, downcomer and recirculating pump of a conventional La Mont loop. Models for the steam and feedwater plant are not derived. (author)
Irvine, M A; Reimer, L J; Njenga, S M; Gunawardena, S; Kelly-Hope, L; Bockarie, M; Hollingsworth, T D
2015-10-22
With ambitious targets to eliminate lymphatic filariasis over the coming years, there is a need to identify optimal strategies to achieve them in areas with different baseline prevalence and stages of control. Modelling can assist in identifying what data should be collected and what strategies are best for which scenarios. We develop a new individual-based, stochastic mathematical model of the transmission of lymphatic filariasis. We validate the model by fitting to a first time point and predicting future timepoints from surveillance data in Kenya and Sri Lanka, which have different vectors and different stages of the control programme. We then simulate different treatment scenarios in low, medium and high transmission settings, comparing once yearly mass drug administration (MDA) with more frequent MDA and higher coverage. We investigate the potential impact that vector control, systematic non-compliance and different levels of aggregation have on the dynamics of transmission and control. In all settings, increasing coverage from 65 to 80 % has a similar impact on control to treating twice a year at 65 % coverage, for fewer drug treatments being distributed. Vector control has a large impact, even at moderate levels. The extent of aggregation of parasite loads amongst a small portion of the population, which has been estimated to be highly variable in different settings, can undermine the success of a programme, particularly if high risk sub-communities are not accessing interventions. Even moderate levels of vector control have a large impact both on the reduction in prevalence and the maintenance of gains made during MDA, even when parasite loads are highly aggregated, and use of vector control is at moderate levels. For the same prevalence, differences in aggregation and adherence can result in very different dynamics. The novel analysis of a small amount of surveillance data and resulting simulations highlight the need for more individual level data to be
Winskill, Peter; Harrison, Wendy E; French, Michael D; Dixon, Matthew A; Abela-Ridder, Bernadette; Basáñez, María-Gloria
2017-02-09
The pork tapeworm, Taenia solium, and associated human infections, taeniasis, cysticercosis and neurocysticercosis, are serious public health problems, especially in developing countries. The World Health Organization (WHO) has set goals for having a validated strategy for control and elimination of T. solium taeniasis/cysticercosis by 2015 and interventions scaled-up in selected countries by 2020. Timely achievement of these internationally-endorsed targets requires that the relative benefits and effectiveness of potential interventions be explored rigorously within a quantitative framework. A deterministic, compartmental transmission model (EPICYST) was developed to capture the dynamics of the taeniasis/cysticercosis disease system in the human and pig hosts. Cysticercosis prevalence in humans, an outcome of high epidemiological and clinical importance, was explicitly modelled. A next generation matrix approach was used to derive an expression for the basic reproduction number, R 0 . A full sensitivity analysis was performed using a methodology based on Latin-hypercube sampling partial rank correlation coefficient index. EPICYST outputs indicate that chemotherapeutic intervention targeted at humans or pigs would be highly effective at reducing taeniasis and cysticercosis prevalence when applied singly, with annual chemotherapy of humans and pigs resulting, respectively, in 94 and 74% of human cysticercosis cases averted. Improved sanitation, meat inspection and animal husbandry are less effective but are still able to reduce prevalence singly or in combination. The value of R 0 for taeniasis was estimated at 1.4 (95% Credible Interval: 0.5-3.6). Human- and pig-targeted drug-focussed interventions appear to be the most efficacious approach from the options currently available. The model presented is a forward step towards developing an informed control and elimination strategy for cysticercosis. Together with its validation against field data, EPICYST will be a
Gerretsen, E.
2000-01-01
Prediction models for the airborne and impact sound transmission in buildings have recently been established (EN 12354- 1&2:1999). However, these models do not cover technical installations and machinery as a source of sound in buildings. Yet these can cause unacceptable sound levels and it is
A simplified mathematical model for scattered transmission of X-rays in raw brown coal
International Nuclear Information System (INIS)
Braune, M.
1983-01-01
A simplified mathematical model is presented which renders it possible to calculate the ash content of lignite from scattered transmission of X radiation taking into account two grain classes, the bulk density, and the fill height. The fine grain is assigned to sand and the coarse one to lignite. The model provides a correlation between the fine grain content and the counting rate
A dynamical model for multifragmentation
International Nuclear Information System (INIS)
Ngo, H.; Ighezou, F.Z.; Ngo, C.
1999-01-01
The surface multifragmentation of highly excited (compression and thermal excitation) 208 Pb is investigated with a finite temperature spherical TDHF approximation coupled to a restructured aggregation model. This approach is discussed in terms of the data available from ALADIN collaboration at GSI on gold ion induced reactions on C, Al and Cu targets at 600 MeV/u excitation energy. The calculation showed that the slowest fragments originate in the nuclear volume while the smaller, faster fragments are emitted from surface
Nonlinear Dynamic Models in Advanced Life Support
Jones, Harry
2002-01-01
To facilitate analysis, ALS systems are often assumed to be linear and time invariant, but they usually have important nonlinear and dynamic aspects. Nonlinear dynamic behavior can be caused by time varying inputs, changes in system parameters, nonlinear system functions, closed loop feedback delays, and limits on buffer storage or processing rates. Dynamic models are usually cataloged according to the number of state variables. The simplest dynamic models are linear, using only integration, multiplication, addition, and subtraction of the state variables. A general linear model with only two state variables can produce all the possible dynamic behavior of linear systems with many state variables, including stability, oscillation, or exponential growth and decay. Linear systems can be described using mathematical analysis. Nonlinear dynamics can be fully explored only by computer simulations of models. Unexpected behavior is produced by simple models having only two or three state variables with simple mathematical relations between them. Closed loop feedback delays are a major source of system instability. Exceeding limits on buffer storage or processing rates forces systems to change operating mode. Different equilibrium points may be reached from different initial conditions. Instead of one stable equilibrium point, the system may have several equilibrium points, oscillate at different frequencies, or even behave chaotically, depending on the system inputs and initial conditions. The frequency spectrum of an output oscillation may contain harmonics and the sums and differences of input frequencies, but it may also contain a stable limit cycle oscillation not related to input frequencies. We must investigate the nonlinear dynamic aspects of advanced life support systems to understand and counter undesirable behavior.
Modelling sexual transmission of HIV: testing the assumptions, validating the predictions
Baggaley, Rebecca F.; Fraser, Christophe
2010-01-01
Purpose of review To discuss the role of mathematical models of sexual transmission of HIV: the methods used and their impact. Recent findings We use mathematical modelling of “universal test and treat” as a case study to illustrate wider issues relevant to all modelling of sexual HIV transmission. Summary Mathematical models are used extensively in HIV epidemiology to deduce the logical conclusions arising from one or more sets of assumptions. Simple models lead to broad qualitative understanding, while complex models can encode more realistic assumptions and thus be used for predictive or operational purposes. An overreliance on model analysis where assumptions are untested and input parameters cannot be estimated should be avoided. Simple models providing bold assertions have provided compelling arguments in recent public health policy, but may not adequately reflect the uncertainty inherent in the analysis. PMID:20543600
System Dynamics Modeling of Multipurpose Reservoir Operation
Directory of Open Access Journals (Sweden)
Ebrahim Momeni
2006-03-01
Full Text Available System dynamics, a feedback – based object – oriented simulation approach, not only represents complex dynamic systemic systems in a realistic way but also allows the involvement of end users in model development to increase their confidence in modeling process. The increased speed of model development, the possibility of group model development, the effective communication of model results, and the trust developed in the model due to user participation are the main strengths of this approach. The ease of model modification in response to changes in the system and the ability to perform sensitivity analysis make this approach more attractive compared with systems analysis techniques for modeling water management systems. In this study, a system dynamics model was developed for the Zayandehrud basin in central Iran. This model contains river basin, dam reservoir, plains, irrigation systems, and groundwater. Current operation rule is conjunctive use of ground and surface water. Allocation factor for each irrigation system is computed based on the feedback from groundwater storage in its zone. Deficit water is extracted from groundwater.The results show that applying better rules can not only satisfy all demands such as Gawkhuni swamp environmental demand, but it can also prevent groundwater level drawdown in future.
Side-coupled cavity model for surface plasmon-polariton transmission across a groove
International Nuclear Information System (INIS)
Liu, J.S.Q.
2010-01-01
We demonstrate that the transmission properties of surface plasmon-polaritons (SPPs) across a rectangular groove in a metallic film can be described by an analytical model that treats the groove as a side-coupled cavity to propagating SPPs on the metal surface. The coupling efficiency to the groove is quantified by treating it as a truncated metal-dielectric-metal (MDM) waveguide. Finite-difference frequency-domain (FDFD) simulations and mode orthogonality relations are employed to derive the basic scattering coefficients that describe the interaction between the relevant modes in the system. The modeled SPP transmission and reflection intensities show excellent agreement with full-field simulations over a wide range of groove dimensions, validating this intuitive model. The model predicts the sharp transmission minima that occur whenever an incident SPP resonantly couples to the groove. We also for the first time show the importance of evanescent, reactive MDM SPP modes to the transmission behavior. SPPs that couple to this mode are resonantly enhanced upon reflection from the bottom of the groove, leading to high field intensities and sharp transmission minima across the groove. The resonant behavior exhibited by the grooves has a number of important device applications, including SPP mirrors, filters, and modulators.
Switched causual modeling of transmission with clutch in hybrid electric vehicles
LHOMME, W; TRIGUI, R; DELARU, P; JEANNERET, B; BOUSCAUROL, A; BADIN, F
2008-01-01
Certain difficulties arise when attempting to model a clutch in a power train transmission due to its nonlinear behavior. Two different states have to be taken into account-the first being when the clutch is locked and the second being when the clutch is slipping. In this paper, a clutch model is developed using the Energetic Macroscopic Representation, which is, in turn, used in the modeling of complete hybrid electric vehicles (HEVs). Two different models are used, and a specific condition ...
Lee, Elizabeth C.; Kelly, Michael R.; Ochocki, Brad M.; Akinwumi, Segun M.; Hamre, Karen E. S.; Tien, Joseph H.; Eisenberg, Marisa C.
2016-01-01
Mathematical models of cholera and waterborne disease vary widely in their structures, in terms of transmission pathways, loss of immunity, and other features. These differences may yield different predictions and parameter estimates from the same data. Given the increasing use of models to inform public health decision-making, it is important to assess distinguishability (whether models can be distinguished based on fit to data) and inference robustness (whether model inferences are robust t...
Modeling and identification in structural dynamics
Jayakumar, Paramsothy
1987-01-01
Analytical modeling of structures subjected to ground motions is an important aspect of fully dynamic earthquake-resistant design. In general, linear models are only sufficient to represent structural responses resulting from earthquake motions of small amplitudes. However, the response of structures during strong ground motions is highly nonlinear and hysteretic. System identification is an effective tool for developing analytical models from experimental data. Testing of full-scale prot...
Feature Extraction for Structural Dynamics Model Validation
Energy Technology Data Exchange (ETDEWEB)
Farrar, Charles [Los Alamos National Laboratory; Nishio, Mayuko [Yokohama University; Hemez, Francois [Los Alamos National Laboratory; Stull, Chris [Los Alamos National Laboratory; Park, Gyuhae [Chonnam Univesity; Cornwell, Phil [Rose-Hulman Institute of Technology; Figueiredo, Eloi [Universidade Lusófona; Luscher, D. J. [Los Alamos National Laboratory; Worden, Keith [University of Sheffield
2016-01-13
As structural dynamics becomes increasingly non-modal, stochastic and nonlinear, finite element model-updating technology must adopt the broader notions of model validation and uncertainty quantification. For example, particular re-sampling procedures must be implemented to propagate uncertainty through a forward calculation, and non-modal features must be defined to analyze nonlinear data sets. The latter topic is the focus of this report, but first, some more general comments regarding the concept of model validation will be discussed.
The AURIC-M Atmospheric Transmission and Radiance Model
1993-01-01
ZAER , ZNEW, and ZNEWV, and used locally to set the array ZMDL for use elsewhere in the program. 3) The user input data layers for Model 7, which...including the layering. For this reason, the original calculation layer altitudes were kept in place (array ZAER ), and new ones were added in a separate...variable (ZAUR), used only when the AURIC mode is on. The ZAER altitudes vary in 1 km steps from 0 to 25 kin, in 5 km steps up through 50 kin, with
Quantum model of light transmission in array waveguide gratings.
Capmany, J; Mora, J; Fernández-Pousa, C R; Muñoz, P
2013-06-17
We develop, to the best of our knowledge, the first model for an array waveguide grating (AWG) device subject to quantum inputs and analyze its basic transformation functionalities for single-photon states. A commercial, cyclic AWG is experimentally characterized with weak input coherent states as a means of exploring its behaviour under realistic quantum detection. In particular it is shown the existence of a cutoff value of the average photon number below which quantum crosstalk between AWG ports is negligible with respect to dark counts. These results can be useful when considering the application of AWG devices to integrated quantum photonic systems.
Record Dynamics and the Parking Lot Model for granular dynamics
Sibani, Paolo; Boettcher, Stefan
Also known for its application to granular compaction (E. Ben-Naim et al., Physica D, 1998), the Parking Lot Model (PLM) describes the random parking of identical cars in a strip with no marked bays. In the thermally activated version considered, cars can be removed at an energy cost and, in thermal equilibrium, their average density increases as temperature decreases. However, equilibration at high density becomes exceedingly slow and the system enters an aging regime induced by a kinematic constraint, the fact that parked cars may not overlap. As parking an extra car reduces the available free space,the next parking event is even harder to achieve. Records in the number of parked cars mark the salient features of the dynamics and are shown to be well described by the log-Poisson statistics known from other glassy systems with record dynamics. Clusters of cars whose positions must be rearranged to make the next insertion possible have a length scale which grows logarithmically with age, while their life-time grows exponentially with size. The implications for a recent cluster model of colloidal dynamics,(S. Boettcher and P. Sibani, J. Phys.: Cond. Matter, 2011 N. Becker et al., J. Phys.: Cond. Matter, 2014) are discussed. Support rom the Villum Foundation is gratefully acknowledged.
Modeling the dynamics of dissent
Lee, Eun; Holme, Petter; Lee, Sang Hoon
2017-11-01
We investigate the formation of opinion against authority in an authoritarian society composed of agents with different levels of authority. We explore a ;dissenting; opinion, held by lower-ranking, obedient, or less authoritative people, spreading in an environment of an ;affirmative; opinion held by authoritative leaders. A real-world example would be a corrupt society where people revolt against such leaders, but it can be applied to more general situations. In our model, agents can change their opinion depending on their authority relative to their neighbors and their own confidence level. In addition, with a certain probability, agents can override the affirmative opinion to take the dissenting opinion of a neighbor. Based on analytic derivation and numerical simulations, we observe that both the network structure and heterogeneity in authority, and their correlation, significantly affect the possibility of the dissenting opinion to spread through the population. In particular, the dissenting opinion is suppressed when the authority distribution is very heterogeneous and there exists a positive correlation between the authority and the number of neighbors of people (degree). Except for such an extreme case, though, spreading of the dissenting opinion takes place when people have the tendency to override the authority to hold the dissenting opinion, but the dissenting opinion can take a long time to spread to the entire society, depending on the model parameters. We argue that the internal social structure of agents sets the scale of the time to reach consensus, based on the analysis of the underlying structural properties of opinion spreading.
Hu, Eric Y; Bouteiller, Jean-Marie C; Song, Dong; Baudry, Michel; Berger, Theodore W
2015-01-01
Chemical synapses are comprised of a wide collection of intricate signaling pathways involving complex dynamics. These mechanisms are often reduced to simple spikes or exponential representations in order to enable computer simulations at higher spatial levels of complexity. However, these representations cannot capture important nonlinear dynamics found in synaptic transmission. Here, we propose an input-output (IO) synapse model capable of generating complex nonlinear dynamics while maintaining low computational complexity. This IO synapse model is an extension of a detailed mechanistic glutamatergic synapse model capable of capturing the input-output relationships of the mechanistic model using the Volterra functional power series. We demonstrate that the IO synapse model is able to successfully track the nonlinear dynamics of the synapse up to the third order with high accuracy. We also evaluate the accuracy of the IO synapse model at different input frequencies and compared its performance with that of kinetic models in compartmental neuron models. Our results demonstrate that the IO synapse model is capable of efficiently replicating complex nonlinear dynamics that were represented in the original mechanistic model and provide a method to replicate complex and diverse synaptic transmission within neuron network simulations.
Modeling Dynamic Regulatory Processes in Stroke
McDermott, Jason E.; Jarman, Kenneth; Taylor, Ronald; Lancaster, Mary; Shankaran, Harish; Vartanian, Keri B.; Stevens, Susan L.; Stenzel-Poore, Mary P.; Sanfilippo, Antonio
2012-01-01
The ability to examine the behavior of biological systems in silico has the potential to greatly accelerate the pace of discovery in diseases, such as stroke, where in vivo analysis is time intensive and costly. In this paper we describe an approach for in silico examination of responses of the blood transcriptome to neuroprotective agents and subsequent stroke through the development of dynamic models of the regulatory processes observed in the experimental gene expression data. First, we identified functional gene clusters from these data. Next, we derived ordinary differential equations (ODEs) from the data relating these functional clusters to each other in terms of their regulatory influence on one another. Dynamic models were developed by coupling these ODEs into a model that simulates the expression of regulated functional clusters. By changing the magnitude of gene expression in the initial input state it was possible to assess the behavior of the networks through time under varying conditions since the dynamic model only requires an initial starting state, and does not require measurement of regulatory influences at each time point in order to make accurate predictions. We discuss the implications of our models on neuroprotection in stroke, explore the limitations of the approach, and report that an optimized dynamic model can provide accurate predictions of overall system behavior under several different neuroprotective paradigms. PMID:23071432
Assessing the role of landscape connectivity on Opisthorchis viverrini transmission dynamics.
Wang, Yi-Chen; Yuen, Roy; Feng, Chen-Chieh; Sithithaworn, Paiboon; Kim, Ick-Hoi
2017-08-01
Opisthorchis viverrini (Ov) is one of the most important human parasitic diseases in Southeast Asia. Although the concept of connectivity is widely used to comprehend disease dispersal, knowledge of the influences of landscape connectivity on Ov transmission is still rudimentary. This study aimed to investigate the role of landscape connectivity in Ov transmission between the human and the first intermediate snail hosts. Fieldwork was conducted in three villages respectively in Kamalasai District, Kalasin Province, Phu Wiang District, Khon Kaen Province, and Nong Saeng District, Udon Thani Province. Bithynia snails were collected to examine parasitic infections, water samples were analyzed for fecal contamination, and locations of septic tanks and connections between habitat patches with observable water movement were surveyed. Euclidean distance, topological link and distance, and graph measures were employed to quantify the connectivity between human and snail habitats. The findings showed that snail patches with higher fecal contents were generally located nearer to septic tanks. The statistically significant results for the topological link and distance measures highlighted the importance of water in functionally facilitating Ov transmission. Graph measures revealed differences in landscape connectivity across the sites. The site with the largest landscape component size and the most mutually connected snail patches coincided with the presence of Ov parasite, reinforcing its higher risk for human to snail transmission. The site with the dissected landscape structure potentially limited the transmission. This study underscored the potential effect of landscape connectivity on Ov transmission, contributing to the understanding of the spatial variation of Ov infection risk. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
Coupling population dynamics with earth system models: the POPEM model.
Navarro, Andrés; Moreno, Raúl; Jiménez-Alcázar, Alfonso; Tapiador, Francisco J
2017-09-16
Precise modeling of CO 2 emissions is important for environmental research. This paper presents a new model of human population dynamics that can be embedded into ESMs (Earth System Models) to improve climate modeling. Through a system dynamics approach, we develop a cohort-component model that successfully simulates historical population dynamics with fine spatial resolution (about 1°×1°). The population projections are used to improve the estimates of CO 2 emissions, thus transcending the bulk approach of existing models and allowing more realistic non-linear effects to feature in the simulations. The module, dubbed POPEM (from Population Parameterization for Earth Models), is compared with current emission inventories and validated against UN aggregated data. Finally, it is shown that the module can be used to advance toward fully coupling the social and natural components of the Earth system, an emerging research path for environmental science and pollution research.
Dynamical properties of the Rabi model
International Nuclear Information System (INIS)
Hu, Binglu; Zhou, Huili; Chen, Shujie; Xianlong, Gao; Wang, Kelin
2017-01-01
We study the dynamical properties of the quantum Rabi model using a systematic expansion method. Based on the observation that the parity symmetry of the Rabi model is kept during evolution of the states, we decompose the initial state and the time-dependent one into positive and negative parity parts expanded by superposition of the coherent states. The evolutions of the corresponding positive and the negative parities are obtained, in which the expansion coefficients in the dynamical equations are known from the derived recurrence relation. (paper)
An Epidemiological Model of Rift Valley Fever with Spatial Dynamics
Directory of Open Access Journals (Sweden)
Tianchan Niu
2012-01-01
Full Text Available As a category A agent in the Center for Disease Control bioterrorism list, Rift Valley fever (RVF is considered a major threat to the United States (USA. Should the pathogen be intentionally or unintentionally introduced to the continental USA, there is tremendous potential for economic damages due to loss of livestock, trade restrictions, and subsequent food supply chain disruptions. We have incorporated the effects of space into a mathematical model of RVF in order to study the dynamics of the pathogen spread as affected by the movement of humans, livestock, and mosquitoes. The model accounts for the horizontal transmission of Rift Valley fever virus (RVFV between two mosquito and one livestock species, and mother-to-offspring transmission of virus in one of the mosquito species. Space effects are introduced by dividing geographic space into smaller patches and considering the patch-to-patch movement of species. For each patch, a system of ordinary differential equations models fractions of populations susceptible to, incubating, infectious with, or immune to RVFV. The main contribution of this work is a methodology for analyzing the likelihood of pathogen establishment should an introduction occur into an area devoid of RVF. Examples are provided for general and specific cases to illustrate the methodology.
Dynamic Modeling of ThermoFluid Systems
DEFF Research Database (Denmark)
Jensen, Jakob Munch
2003-01-01
The objective of the present study has been to developed dynamic models for two-phase flow in pipes (evaporation and condensation). Special attention has been given to modeling evaporators for refrigeration plant particular dry-expansion evaporators. Models of different complexity have been...... formulated. The different models deviate with respect to the detail¿s included and calculation time in connection with simulation. The models have been implemented in a new library named ThermoTwoPhase to the programming language Modelica. A test rig has been built with an evaporator instrumented in a way...
Research on nonlinear stochastic dynamical price model
International Nuclear Information System (INIS)
Li Jiaorui; Xu Wei; Xie Wenxian; Ren Zhengzheng
2008-01-01
In consideration of many uncertain factors existing in economic system, nonlinear stochastic dynamical price model which is subjected to Gaussian white noise excitation is proposed based on deterministic model. One-dimensional averaged Ito stochastic differential equation for the model is derived by using the stochastic averaging method, and applied to investigate the stability of the trivial solution and the first-passage failure of the stochastic price model. The stochastic price model and the methods presented in this paper are verified by numerical studies
Modeling transmission parameters of polymer microstructured fibers for applications in FTTH networks
Gdula, P.; Welikow, K.; Szczepański, P.; Buczyński, R.; Piramidowicz, R.
2011-10-01
This paper is focused on selected aspects of designing and modeling of transmission parameters of plastic optical fibers (POFs), considered in the context of their potential applications in optical access networks and, specifically, in Fiber-To- The-Home (FTTH) systems. The survey of state-of-the-art solutions is presented and possibility of improving transmission properties of POFs by microstructurization is discussed on the basis of the first results of numerical modeling. In particular, the microstructured POF was designed supporting propagation of limited number of modes while keeping relatively large mode area and, simultaneously, significantly lowered bending losses.
Modelling environmental dynamics. Advances in goematic solutions
Energy Technology Data Exchange (ETDEWEB)
Paegelow, Martin [Toulouse-2 Univ., 31 (France). GEODE UMR 5602 CNRS; Camacho Olmedo, Maria Teresa (eds.) [Granada Univ (Spain). Dpto. de Analisis Geografico Regional y Geografia Fisica
2008-07-01
Modelling environmental dynamics is critical to understanding and predicting the evolution of the environment in response to the large number of influences including urbanisation, climate change and deforestation. Simulation and modelling provide support for decision making in environmental management. The first chapter introduces terminology and provides an overview of methodological modelling approaches which may be applied to environmental and complex dynamics. Based on this introduction this book illustrates various models applied to a large variety of themes: deforestation in tropical regions, fire risk, natural reforestation in European mountains, agriculture, biodiversity, urbanism, climate change and land management for decision support, etc. These case studies, provided by a large international spectrum of researchers and presented in a uniform structure, focus particularly on methods and model validation so that this book is not only aimed at researchers and graduates but also at professionals. (orig.)
Modeling emotional dynamics : currency versus field.
Energy Technology Data Exchange (ETDEWEB)
Sallach, D .L.; Decision and Information Sciences; Univ. of Chicago
2008-08-01
Randall Collins has introduced a simplified model of emotional dynamics in which emotional energy, heightened and focused by interaction rituals, serves as a common denominator for social exchange: a generic form of currency, except that it is active in a far broader range of social transactions. While the scope of this theory is attractive, the specifics of the model remain unconvincing. After a critical assessment of the currency theory of emotion, a field model of emotion is introduced that adds expressiveness by locating emotional valence within its cognitive context, thereby creating an integrated orientation field. The result is a model which claims less in the way of motivational specificity, but is more satisfactory in modeling the dynamic interaction between cognitive and emotional orientations at both individual and social levels.
Ntombela, Nonzwakazi; Mashamba-Thompson, Tivani P; Mtshali, Andile; Voce, Anna; Kharsany, Ayesha B M
2017-01-17
In South Africa, gender inequality dominated by males and heterosexual HIV epidemic are associated with high HIV infection. Underlying epidemiological and social determinants driving HIV acquisition and transmission are critical to understand the extent and complexity of sexual networks as primary mechanisms through which HIV is likely to spread. The aim of the study is to provide an overview of empiric evidence that links the complex interaction of risk of HIV infection in men. We will conduct a systematic scoping review to identify, describe, and map literature on the dynamics of HIV infection in men, and we will determine the quality of the studies reporting on the dynamics of HIV infections in men. Primary research articles, published in peer-reviewed journals, review articles, and gray literature that address the research question, will be included. We will search PubMed, Web of Knowledge, Science Direct, EBSCOhost, Google Scholar, World Health Organization library, and UNAIDS database. Reference lists and existing networks such as government organizations and conferences will also be included to source relevant literature. Two independent reviewers will extract data in parallel from all relevant search engines, using specific inclusion and exclusion criteria. A thematic content analysis will be used to present the narrative account of the reviews, using NVivo version 10. We anticipate finding relevant literature on the dynamics of HIV transmission in South African men. Once summarized, data will be useful to guide future research. PROSPERO CRD42016039489.
Solar radiation transmissivity of a single-span greenhouse through measurements on scale models
International Nuclear Information System (INIS)
Papadakis, G.; Manolakos, D.; Kyritsis, S.
1998-01-01
The solar transmissivity of a single-span greenhouse has been investigated experimentally using a scale model, of dimensions 40 cm width and 80 cm length. The solar transmissivity was measured at 48 positions on the “ground” surface of the scale model using 48 small silicon solar cells. The greenhouse model was positioned horizontally on a specially made goniometric mechanism. In this way, the greenhouse azimuth could be changed so that typical days of the year could be simulated using different combinations of greenhouse azimuth and the position of the sun in the sky. The measured solar transmissivity distribution at the “ground” surface and the average greenhouse solar transmissivity are presented and analysed, for characteristic days of the year, for winter and summer for a latitude of 37°58′ (Athens, Greece). It is shown that for the latitude of 37°58′ N during winter, the E–W orientation is preferable to the N–S one. The side walls, and especially the East and West ones for the E–W orientation, reduce considerably the greenhouse transmissivity at areas close to the walls for long periods of the day when the angle of incidence of the solar rays to these walls is large. (author)
Network flow model of force transmission in unbonded and bonded granular media.
Tordesillas, Antoinette; Tobin, Steven T; Cil, Mehmet; Alshibli, Khalid; Behringer, Robert P
2015-06-01
An established aspect of force transmission in quasistatic deformation of granular media is the existence of a dual network of strongly versus weakly loaded particles. Despite significant interest, the regulation of strong and weak forces through the contact network remains poorly understood. We examine this aspect of force transmission using data on microstructural fabric from: (I) three-dimensional discrete element models of grain agglomerates of bonded subspheres constructed from in situ synchrotron microtomography images of silica sand grains under unconfined compression and (II) two-dimensional assemblies of unbonded photoelastic circular disks submitted to biaxial compression under constant volume. We model force transmission as a network flow and solve the maximum flow-minimum cost (MFMC) problem, the solution to which yields a percolating subnetwork of contacts that transmits the "maximum flow" (i.e., the highest units of force) at "least cost" (i.e., the dissipated energy from such transmission). We find the MFMC describes a two-tier hierarchical architecture. At the local level, it encapsulates intraconnections between particles in individual force chains and in their conjoined 3-cycles, with the most common configuration having at least one force chain contact experiencing frustrated rotation. At the global level, the MFMC encapsulates interconnections between force chains. The MFMC can be used to predict most of the force chain particles without need for any information on contact forces, thereby suggesting the network flow framework may have potential broad utility in the modeling of force transmission in unbonded and bonded granular media.
Stochastic Modeling of Direct Radiation Transmission in Particle-Laden Turbulent Flows
Banko, Andrew; Villafane, Laura; Kim, Ji Hoon; Esmaily Moghadam, Mahdi; Eaton, John K.
2017-11-01
Direct radiation transmission in turbulent flows laden with heavy particles plays a fundamental role in systems such as clouds, spray combustors, and particle-solar-receivers. Owing to their inertia, the particles preferentially concentrate and the resulting voids and clusters lead to deviations in mean transmission from the classical Beer-Lambert law for exponential extinction. Additionally, the transmission fluctuations can exceed those of Poissonian media by an order of magnitude, which implies a gross misprediction in transmission statistics if the correlations in particle positions are neglected. On the other hand, tracking millions of particles in a turbulence simulation can be prohibitively expensive. This work presents stochastic processes as computationally cheap reduced order models for the instantaneous particle number density field and radiation transmission therein. Results from the stochastic processes are compared to Monte Carlo Ray Tracing (MCRT) simulations using the particle positions obtained from the point-particle DNS of isotropic turbulence at a Taylor Reynolds number of 150. Accurate transmission statistics are predicted with respect to MCRT by matching the mean, variance, and correlation length of DNS number density fields. Funded by the U.S. Department of Energy under Grant No. DE-NA0002373-1 and the National Science Foundation under Grant No. DGE-114747.
Between-group transmission dynamics of the swallow bug, Oeciacus vicarius.
Brown, Charles R; Brown, Mary Bomberger
2005-06-01
The parasitic cimicid swallow bug, Oeciacus vicarius, is the principal invertebrate vector for Buggy Creek virus (BCRV) and has also been associated with Venezuelan equine encephalitis virus. To help understand the spread of this vector, we experimentally measured the transmission of O. vicarius between groups (colonies) of its main host, the cliff swallow (Petrochelidonpyrrhonota), in the field. Transmission of bugs between colonies varied significantly with year, size of the colony, and week within the season. Bug immigration into sites tended to peak in mid-summer. Swallow nests in larger colonies had more consistent rates of bug introduction than did nests in small colonies, but within a colony a given nest's weekly immigrant-bug count varied widely across the season. Transmission of O. vicarius between host social groups follows broadly predictable seasonal patterns, but there is nevertheless temporal and spatial heterogeneity in bug transmission. By understanding how long-distance movement by this vector varies in time and space, we can better predict where and when BCRV epizootics may occur.
Koizumi, Schuichi; Fujishita, Kayoko; Tsuda, Makoto; Shigemoto-Mogami, Yukari; Inoue, Kazuhide
2003-09-01
Originally ascribed passive roles in the CNS, astrocytes are now known to have an active role in the regulation of synaptic transmission. Neuronal activity can evoke Ca2+ transients in astrocytes, and Ca2+ transients in astrocytes can evoke changes in neuronal activity. The excitatory neurotransmitter glutamate has been shown to mediate such bidirectional communication between astrocytes and neurons. We demonstrate here that ATP, a primary mediator of intercellular Ca2+ signaling among astrocytes, also mediates intercellular signaling between astrocytes and neurons in hippocampal cultures. Mechanical stimulation of astrocytes evoked Ca2+ waves mediated by the release of ATP and the activation of P2 receptors. Mechanically evoked Ca2+ waves led to decreased excitatory glutamatergic synaptic transmission in an ATP-dependent manner. Exogenous application of ATP does not affect postsynaptic glutamatergic responses but decreased presynaptic exocytotic events. Finally, we show that astrocytes exhibit spontaneous Ca2+ waves mediated by extracellular ATP and that inhibition of these Ca2+ responses enhanced excitatory glutamatergic transmission. We therefore conclude that ATP released from astrocytes exerts tonic and activity-dependent down-regulation of synaptic transmission via presynaptic mechanisms.
Modeling initial contact dynamics during ambulation with dynamic simulation.
Meyer, Andrew R; Wang, Mei; Smith, Peter A; Harris, Gerald F
2007-04-01
Ankle-foot orthoses are frequently used interventions to correct pathological gait. Their effects on the kinematics and kinetics of the proximal joints are of great interest when prescribing ankle-foot orthoses to specific patient groups. Mathematical Dynamic Model (MADYMO) is developed to simulate motor vehicle crash situations and analyze tissue injuries of the occupants based multibody dynamic theories. Joint kinetics output from an inverse model were perturbed and input to the forward model to examine the effects of changes in the internal sagittal ankle moment on knee and hip kinematics following heel strike. Increasing the internal ankle moment (augmentation, equivalent to gastroc-soleus contraction) produced less pronounced changes in kinematic results at the hip, knee and ankle than decreasing the moment (attenuation, equivalent to gastroc-soleus relaxation). Altering the internal ankle moment produced two distinctly different kinematic curve morphologies at the hip. Decreased internal ankle moments increased hip flexion, peaking at roughly 8% of the gait cycle. Increasing internal ankle moments decreased hip flexion to a lesser degree, and approached normal at the same point in the gait cycle. Increasing the internal ankle moment produced relatively small, well-behaved extension-biased kinematic results at the knee. Decreasing the internal ankle moment produced more substantial changes in knee kinematics towards flexion that increased with perturbation magnitude. Curve morphologies were similar to those at the hip. Immediately following heel strike, kinematic results at the ankle showed movement in the direction of the internal moment perturbation. Increased internal moments resulted in kinematic patterns that rapidly approach normal after initial differences. When the internal ankle moment was decreased, differences from normal were much greater and did not rapidly decrease. This study shows that MADYMO can be successfully applied to accomplish forward
Modeling and Dynamic Analysis of Cutterhead Driving System in Tunnel Boring Machine
Directory of Open Access Journals (Sweden)
Wei Sun
2017-01-01
Full Text Available Failure of cutterhead driving system (CDS of tunnel boring machine (TBM often occurs under shock and vibration conditions. To investigate the dynamic characteristics and reduce system vibration further, an electromechanical coupling model of CDS is established which includes the model of direct torque control (DTC system for three-phase asynchronous motor and purely torsional dynamic model of multistage gear transmission system. The proposed DTC model can provide driving torque just as the practical inverter motor operates so that the influence of motor operating behavior will not be erroneously estimated. Moreover, nonlinear gear meshing factors, such as time-variant mesh stiffness and transmission error, are involved in the dynamic model. Based on the established nonlinear model of CDS, vibration modes can be classified into three types, that is, rigid motion mode, rotational vibration mode, and planet vibration mode. Moreover, dynamic responses under actual driving torque and idealized equivalent torque are compared, which reveals that the ripple of actual driving torque would aggravate vibration of gear transmission system. Influence index of torque ripple is proposed to show that vibration of system increases with torque ripple. This study provides useful guideline for antivibration design and motor control of CDS in TBM.