Dynamic increasing returns and innovation diffusion: bringing Polya Urn processes to the empirical data

The patterns of innovation diffusion are well approximated by the logistic curves. This is the robust empirical fact confirmed by many studies in innovations dynamics. Here, we show that the logistic pattern of innovation diffusion can be replicated by the time-dependent stochastic process with positive feedbacks along the diffusion trajectory. The dynamic increasing returns process is modelled by Polya Urns. So far, Urn models have been mostly used to study the [path-dependent] limit properties. On the contrary, this work focuses on the transient [finite time] properties studying the conditions under which urn models capture the logistic trajectories which often track empirical diffusion process. As examples, we calibrate the process to match several cases of diffusion of motor ships in European countries.     

Modeling of non-equilibrium solute diffusion upon rapid solidification: effective mobility versus kinetic energy

Abstract

The effective mobility approach is compared with the kinetic energy approach in terms of sharp interface modeling and phase-field modelling of non-equilibrium solute diffusion upon rapid solidification of binary alloys. The two approaches are equivalent for modelling of long range solute diffusion in bulk phases, but only the effective mobility approach can introduce the non-equilibrium solute diffusion effect to short range solute diffusion at a sharp interface or within a diffuse interface. Addition of the kinetic energy terms results in an unreasonable non-bilinear expression of the flux and thermodynamic driving force in the free energy production of interface migration or phase field propagation, whereas the effective mobility approach allows the thermodynamic extremal principle workable.     

生物微胶囊传递模型的研究

以ＡＰＡ生物微胶囊的研究对象，建立了微胶囊的球形非稳态渗透扩散模型；通过分析各准数间的关系，可以较为全面地了解膜内传质规律，利用实验数据拟合，可以求算膜相有效扩散系数，并能预测膜内浓度分布。     

Entrepreneurs and technology diffusion: How diffusion research can benefit from a greater understanding of entrepreneurship

This study builds on the work of Schumpeter and others who have recognised the role of entrepreneurs in the formation of entirely new industries around technological innovation. With this in mind, it critically reviews diffusion research, finding this work to be lacking in its treatment of entrepreneurship and its ability to integrate the wide range of factors that affect the diffusion process. In an effort to address these theoretical gaps, this study draws on management literature on the growth of the entrepreneurial firm, which puts entrepreneurs at the centre of analysis, and serves to integrate many of the traditional concerns of diffusion research. The authors hope that the proposed analytical framework will be applied to future case studies of technology diffusion in order that we might continue to better understand and explain the rate of technological advance in society.     

Modelling seasonal influenza: the role of weather and punctuated antigenic drift

Seasonal influenza appears as annual oscillations in temperate regions of the world, yet little is known as to what drives these annual outbreaks and what factors are responsible for their inter-annual variability. Recent studies suggest that weather variables, such as absolute humidity, are the key drivers of annual influenza outbreaks. The rapid, punctuated, antigenic evolution of the influenza virus is another major factor. We present a new framework for modelling seasonal influenza based on a discrete-time, age-of-infection, epidemic model, which allows the calculation of the model''s likelihood function in closed form. This framework may be used to perform model inference and parameter estimation rigorously. The modelling approach allows us to fit 11 years of Israeli influenza data, with the best models fitting the data with unusually high correlations in which r > 0.9. We show that using actual weather to modulate influenza transmission rate gives better results than using the inter-annual means of the weather variables, providing strong support for the role of weather in shaping the dynamics of influenza. This conclusion remains valid even when incorporating a more realistic depiction of the decay of immunity at the population level, which allows for discrete changes in immunity from year to year.     

Modelling area-wide count outcomes with spatial correlation and heterogeneity: an analysis of London crash data

Count models such as negative binomial (NB) regression models are normally employed to establish a relationship between area-wide traffic crashes and the contributing factors. Since crash data are collected with reference to location measured as points in space, spatial dependence exists among the area-level crash observations. Although NB models can take account of the effect of unobserved heterogeneity (due to omitted variables in the model) among neighbourhoods, such models may not account for spatial correlation areas. It is then essential to adopt an econometric model that takes account of both spatial dependence and uncorrelated heterogeneity simultaneously among neighbouring units. In studying the spatial pattern of traffic crashes, two types of spatial models may be employed: (i) classical spatial models for higher levels of spatial aggregation such as states, counties, etc. and (ii) Bayesian hierarchical models for all spatial units, especially for smaller scale area-aggregations. Therefore, the primary objectives of this paper is to develop a series of relationships between area-wide different traffic casualties and the contributing factors associated with ward characteristics using both non-spatial models (such as NB models) and spatial models and to identify the similarities and differences among these relationships. The spatial units of the analysis are the 633 census wards from the Greater London metropolitan area. Ward-level casualty data are disaggregated by severity of the casualty (such as fatalities, serious injuries, and slight injuries) and by severity of the casualty related to various road users. The analysis implies that different ward-level factors affect traffic casualties differently. The results also suggest that Bayesian hierarchical models are more appropriate in developing a relationship between area-wide traffic crashes and the contributing factors associated with the road infrastructure, socioeconomic and traffic conditions of the area. This is because Bayesian models accurately take account of both spatial dependence and uncorrelated heterogeneity.     

The effect of diffusion processes on the interaction in multicomponent silicate systems

The results of studying diffusion processes in silicate multicomponent systems, which are widely used as binders in variously purposed composite materials, have been generalized and described. It has been shown that the effective diffusion coefficients of alkali and alkaline-earth cations in a diffusion pair are not a single-valued function of the ion radius of the cation but depend on structural factors and on the energy of the cation bonding with other ions of the melt.     

Identifying barriers to wind energy diffusion in Colombia: A function analysis of the technological innovation system and the wider context

By utilizing only half of its total technical wind energy potential, Colombia would be able to supply the entire country's demand for electricity. Yet, Colombia has an installed capacity of 19.5 MW from wind power, representing about 0.4% of the total technical potential. In this paper, the slow diffusion of wind energy in Colombia is analyzed, by evaluating the functions of the Technological Innovation System (TIS) along with the influence of the wider context (Landscape Factors). A combination of expert evaluations (structured and semi-structured interviews) and a history event analysis revealed existing weaknesses in the TIS functions and influence from the wider context (landscape level). Several factors at the landscape level were found to have a significant influence on the TIS functions for wind energy in Colombia. Policy recommendations are provided to address barriers in order to advance the diffusion of wind energy in Colombia.     

论GIS空间关系描述中存在的几个基本问题

首先剖析了空间关系描述中"空间"的概念,论述了拓扑关系具有与实体位置本身无关的特性,进而阐述了空间实体的拓扑表达,分析了拓扑空间描述存在的不足,以及与地理环境、地理空间认知的相关性,提出了纳入度量特性的拓扑空间关系描述的方法。     

Dialectics of nature: Temporal and spatial regulation in material sciences

The cooperative interaction distance measure has been proposed as a novel law pertaining to dialectics of nature,and has been extensively carried out in the design of functional nanomaterials.However,the temporal and spatial dimensions are akin to yin and yang,and thus temporal regulation needs to be accounted for when implementing the above-mentioned principle.Here,we summarize recent advances in temporally and spatially regulated materials and devices.We showcase the temporal regulation of organic semiconductors for organic photovoltaics (OPVs) using the example of exciton lifetime manipulation.As an example of spatial regulation,we consider the distribution of charge carriers in core-shell quantum dot (QD) nanocrystals for modulating their optical properties.Long exciton lifetime can in principle increase the exciton diffussion length,which is desiable for high-efficiency large-area OPV devices.Spatially regulated QDs are highly valuable emitters for light-emitting applications.We aim to show that cooperative spatio-temporal regulation of nanomaterils is of vital importance to the development of functional devices.     

Corneal critical barrier against the penetration of dexamethasone and lomefloxacin hydrochloride: evaluation by the activation energy for drug partition and diffusion in cornea

The cornea is a solid barrier against drug permeation. We searched the critical barrier of corneal drug permeation using a hydrophobic drug, dexamethasone (DM), and a hydrophilic drug, lomefloxacin hydrochloride (LFLX). The activation energies for permeability of DM and LFLX across the intact cornea were 88.0 and 42.1 kJ/mol, respectively. Their activation energies for permeability across the cornea without epithelium decreased to 33.1 and 16.6 kJ/mol, respectively. The results show that epithelium is the critical barrier on the cornea against the permeation of a hydrophobic drug of DM as well as a hydrophilic drug of LFLX. The activation energy of partition for DM (66.8 kJ/mol) was approximately 3-fold larger than that of diffusion (21.2 kJ/mol). The results indicate that the partition for the hydrophobic drug of DM to the corneal epithelium is the primary barrier. Thermodynamic evaluation of activation energy for the drug permeation parameters is a good approch to investigate the mechanism of drug permeability.     

Health technology diffusion: Case of remote patient monitoring (RPM) for the care of senior population

Increase in population is causing further increase in senior population which is the major cost factor in health care. Health information technology has been cited as one of the tools to help reduce this cost for this group of patients. Therefore, our study explores strategies and policies helping reduce the barriers for the adoption of a health information technology – teleconsultation – for senior population. The objective of this research is to develop a model to evaluate alternative solutions to increase the adoption of Remote Patient Monitoring (RPM) for the senior population. The research leverages hierarchical decision modeling (HDM) to build a hierarchical multi criteria assessment model. The model elements are derived through literature and validated by an expert panel.     

On the diffusion of mobile phone innovations for financial inclusion

This article investigates nexuses between innovations in mobile money and financial inclusion. Demand and supply factors that affect the diffusion of mobile services as well as macro-level institutional and economic factors are taken in account. The focus is on 148 countries with data mostly consisting of 2010–2014 averages. The empirical evidence is based on Tobit regressions. The study finds that when the empirical analysis is robust to multicollinearity, two main tendencies are apparent: the significant findings of Lashitew et al. (2019) [1] are confirmed and many new significant estimated coefficients emerge. While this study confirms the findings of the underlying research, it also goes further to improve the harmony in narratives between the predictors and the outcome variables. Accordingly, by accounting for multicollinearity, the earlier findings are now more consistent across the set of predictors (i.e. demand and supply factors) and the attendant financial inclusion outcomes (i.e. mobile money accounts, mobile used to send money and mobile used to receive money).     

Modelling the effectiveness and risks of vaccination strategies to control classical swine fever epidemics

In a recent update of the Dutch contingency plan for controlling outbreaks of classical swine fever (CSF), emergency vaccination is preferred to large-scale pre-emptive culling. This policy change raised two questions: can emergency vaccination be as effective as pre-emptive culling, and what are the implications for showing freedom of infection? Here, we integrate quantitative information available on CSF virus transmission and vaccination effects into a stochastic mathematical model that describes the transmission dynamics at the level of animals, farms and livestock areas. This multilevel approach connects individual-level interventions to large-scale effects. Using this model, we compare the performance of five different control strategies applied to hypothetical CSF epidemics in The Netherlands and, for each of these strategies, we study the properties of three different screening scenarios to show freedom of infection. We find that vaccination in a ring of 2 km radius around a detected infection source is as effective as ring culling in a 1 km radius. Feasible screening scenarios, adapted to the use of emergency vaccination, can reduce the enhanced risks of (initially) undetected farm outbreaks by targeting vaccinated farms. Altogether, our results suggest that emergency vaccination against CSF can be equally effective and safe as pre-emptive culling.     

从第七届国际真空展看扩散泵产品的变化

评述现有国产扩散泵产品的进展情况,存在的不足之处,今后应努力改进的方向.讨论测量扩散泵返油率的几种方法,提出采用石英晶体振荡器测量扩散泵返油率的新建议.     

A reduced order model‐based preconditioner for the efficient solution of transient diffusion equations

This paper presents a novel class of preconditioners for the iterative solution of the sequence of symmetric positive‐definite linear systems arising from the numerical discretization of transient parabolic and self‐adjoint partial differential equations. The preconditioners are obtained by nesting appropriate projections of reduced‐order models into the classical iteration of the preconditioned conjugate gradient (PCG). The main idea is to employ the reduced‐order solver to project the residual associated with the conjugate gradient iterations onto the space spanned by the reduced bases. This approach is particularly appealing for transient systems where the full‐model solution has to be computed at each time step. In these cases, the natural reduced space is the one generated by full‐model solutions at previous time steps. When increasing the size of the projection space, the proposed methodology highly reduces the system conditioning number and the number of PCG iterations at every time step. The cost of the application of the preconditioner linearly increases with the size of the projection basis, and a trade‐off must be found to effectively reduce the PCG computational cost. The quality and efficiency of the proposed approach is finally tested in the solution of groundwater flow models. © 2016 The Authors. International Journal for Numerical Methods in Engineering Published by John Wiley & Sons Ltd.