S-shaped Growth Research Articles

Adoption of telemedicine: from pilot stage to routine delivery

BackgroundToday there is much debate about why telemedicine has stalled. Teleradiology is the only widespread telemedicine application. Other telemedicine applications appear to be promising candidates for widespread use, but they remain in the early adoption stage. The objective of this debate paper is to achieve a better understanding of the adoption of telemedicine, to assist those trying to move applications from pilot stage to routine delivery.DiscussionWe have investigated the reasons why telemedicine has stalled by focusing on two, high-level topics: 1) the process of adoption of telemedicine in comparison with other technologies; and 2) the factors involved in the widespread adoption of telemedicine. For each topic, we have formulated hypotheses. First, the advantages for users are the crucial determinant of the speed of adoption of technology in healthcare. Second, the adoption of telemedicine is similar to that of other health technologies and follows an S-shaped logistic growth curve. Third, evidence of cost-effectiveness is a necessary but not sufficient condition for the widespread adoption of telemedicine. Fourth, personal incentives for the health professionals involved in service provision are needed before the widespread adoption of telemedicine will occur.SummaryThe widespread adoption of telemedicine is a major -- and still underdeveloped -- challenge that needs to be strengthened through new research directions. We have formulated four hypotheses, which are all susceptible to experimental verification. In particular, we believe that data about the adoption of telemedicine should be collected from applications implemented on a large-scale, to test the assumption that the adoption of telemedicine follows an S-shaped growth curve. This will lead to a better understanding of the process, which will in turn accelerate the adoption of new telemedicine applications in future. Research is also required to identify suitable financial and professional incentives for potential telemedicine users and understand their importance for widespread adoption.

The early diffusion of the steam engine in Britain, 1700–1800: a reappraisal

We examine the diffusion of steam technology across British counties during the eighteenth century. First, we provide new estimates for the regional variations in the timing, pace and extent of usage of steam engines. Our main data source is an updated version of the list of steam engines erected in Britain during the eighteenth century originally compiled by Kanefsky and Robey (Technol Cult 21:161–186, 1980). Following a rather established approach for analysing the diffusion of new technologies we fit S-shaped growth functions to the data on the numbers of steam engines installed in each county. In this way, we are able to provide a comprehensive appraisal of the relative speed of the diffusion process in different counties. Second, in order to assess the relative importance of the variables shaping the diffusion of steam power technology, we study the relationship between the number of steam engines installed in each county and localization factors such as coal prices, availability of water sites, number of textile mills and number of blast furnaces.

Comparison of Predictive Capability of Software Reliability Growth Models with Exponentiated Weibull Distribution

This study aims to compare the predictive capability of two popular software reliability growth models (SRGM), say exponential growth and inflection S-shaped growth models. We first review the exponentiated Weibull (EW) testing-effort functions and discuss exponential type and inflection S-shaped type SRGM with EW testing-effort. We then analyzed the actual data applications and compare the predictive capability of these two SRGM graphically. The findings reveal that inflection Sshaped type SRGM has better prediction capability as compare to exponential type SRGM.

Biosorption of cadmium ions using Pleurotus ostreatus: Growth kinetics, isotherm study and biosorption mechanism

The mycelial growth kinetics, cadmium biosorption capacity and main governing biosorption mechanism of Pleurotus ostreatus (oyster mushroom) have been determined in this study. The fungus mycelium exhibits a sigmoidal (S-shaped) growth curve in which the growth rates for the lag and exponential phases are 0.1 and 0.31 g/L·day, respectively. The grown fungus is subjected to elemental, infra-red and scanning electron microscopy-energy dispersive x-ray spectroscopy analyses, while biosorption data are fitted to established adsorption isotherm models, namely, Langmuir, Freundlich and Dubinin-Radushkevich. It is strongly suggested that the main governing mechanism involved is chemisorption due to good fitting of biosorption data to Langmuir and Dubinin-Radushkevich models with possibility of involvement of both ion exchange and complexation. Data presented in the study are very useful for design of future pilot- or industrial-scale biosorption water purification systems.

Software Reliability Growth Model Based on Half Logistic Distribution

A non-homogeneous Poisson process with its mean value function generated by the cumulative distribution function of half logistic distribution is considered. It is modeled to assess the failure phenomenon of developed software. When the failure data are in the form of the number of failures in a given interval of time, the model parameters are estimated by the maximum likelihood method. The performance of the model is compared with two standard models [Goel, A. L., and Okumoto. K., “A Time Dependent Error Detection Rate Model for Software Reliability and Other Performance Measures,” IEEE Trans. Reliab., Vol. 28(3), 1979, pp. 206–211; Yamada , “S-Shaped Reliability Growth Modeling for Software Error Detection,” IEEE Trans. Reliab., Vol. 32(5), 1983, pp. 475–484] using two data sets. The release time of the software subject to a minimum expected cost is worked out and exemplified through illustrations.

Growth of zirconia particles by heterocoagulation, self-assembly, and convection-induced coagulation during forced hydrolysis in a refluxed reaction vessel

In literature related to forced hydrolysis of zirconia, heterocoagulation between large particulates and primary crystallites is generally accepted as the principal route of growth. Our dynamic light scattering (DLS) results revealed an S-shaped growth curve with the growth rate (slope) varying notably from one stage to the other, implying that other coagulation mechanisms may be present. Time-sequenced side-by-side electron microscopy and DLS analyses were conducted along the curves alongside with field emission scanning electron microscopy of full-grown particles. We find that particles growth follows a two-stage heterocoagulation process with primary crystallites and small particles produced from the first-stage serving as building blocks for the first and second stages, respectively. It interesting to note that growth during the second stage occurs by self-assembly and a hypothesis is proposed. Convection-induced coagulation leads to enhanced particle growth for a low precursor concentration but minimal growth for a higher one, both of which conform to the predictions of Melis et al. [AIChE J. 45, 1383 (1999)].

Bayesian Optimal Release Time Based on Inflection S-Shaped Software Reliability Growth Model

The inflection S-shaped software reliability growth model (SRGM) proposed by Ohba (1984) is one of the well- known SRGMs. This paper deals with the optimal software release problem with regard to the expected software cost under this model based on the Bayesian approach. To reflect the effect of the learning experience for the updated software system, we consider several improvement factors to adjust the values of parameters characterizing the inflection S-shaped SRGM. Appropriate prior distributions are assumed for such factors and the expected total software cost is formulated. The optimal release time is shown to be finite and uniquely determined. Because of the flexibility of prior distributions, the proposed Bayesian methods may be applied in many different situations. Numerical results are presented on the basis of the real data.

The diffusion of mobile phones in India

Mobile phones, which were introduced around a decade ago in 1995–1996 in India, are becoming the dominant means of accessing communication. At the end of 2005–2006, there were 90 million mobile subscribers in India in comparison to 50 million subscribers for landlines. The increase in mobile phones has been phenomenal in comparison with landlines since the introduction of mobiles in the country. The main aim of this paper is to estimate future trends and analyze the pattern and rate of adoption of mobile phones in India. The paper uses S-shaped growth curve models for the same. It is found that mobile-density (number of mobile phones per 100 inhabitants) in India will increase from 8.1 in 2005–2006 to 36.5 in 2010–2011 and 71 in 2015–2016. Consequently, the mobile subscriber base is projected to increase from 90 million in 2005–2006 to 433 million in 2010–2011 and nearly 900 million in 2015–2016. The projected rapid growth in the mobile subscriber base will have important implications for future plans of mobile operators, infrastructure providers, handset suppliers and vendors. Mobile operators should be ready with contingency plans to deploy and operate infrastructure including customer care, billing, applications, etc., faster than that they might have initially planned. Infrastructure providers, handset suppliers and vendors should be prepared to respond to such plans.

A generalized software fault classification model

Most non-homogenous Poisson process (NHPP) based software reliability growth models (SRGMs) presented in the literature assume that the faults in the software are of the same type. However, this assumption is not truly representative of reality. It has been observed that the software contains different types of faults and each fault requires different strategies and different amount of testing-effort to remove it. If this assumption is not taken into account, the SRGM may give misleading results. This paper proposes a generalized model based on classification the faults in the software system according to their removal complexity. The removal complexity is proportional to the amount of testing-effort required to remove the fault. The testing-effort expenditures are represented by the number of stages required to remove the fault after the failure observation / fault isolation (with time delay between the stages). Therefore, it explicitly takes into account the faults of different severity and can capture variability in the growth curves depending on the environment it is being used and at the same time it has the capability to reduce either to exponential or S-shaped growth curves. Such modelling approach is very much suited for object-oriented programming and distributed development environments. Actual software reliability data have been used to demonstrate the proposed generalized model.

Buys-Ballot estimates for exponential and s-shaped growth curves

The Buys-Ballot estimation procedure for time series decomposition when trend-cycle component is either exponential, modified exponential, Gompertz or logistic is discussed in this paper. Estimates are derived for the additive and multiplicative models. A simulated example for the exponential case is used to illustrate the methods developed. Buys-Ballot estimates are compared with the least squares estimates. Journal of the Nigerian Association of Mathematical Physics Vol. 9 2005: pp. 357-366

Modelling and Forecasting the Diffusion of Telephones in India

The main aim of this paper is to estimate the future trend and analyze the pattern and rate of adoption of telephones in India. The paper uses S-shaped growth curve models for the same. It is found that the teledensity in India will increase from 12.6 telephones per 100 inhabitants in 2005-06 to 107.5 telephones per 100 inhabitants in 2015-16. Consequently, telephone subscriber base is projected to increase from 140 million in 2005-06 to 1361 million in 2015-16. Moreover, mobile phone is becoming and will continue to become the dominant means for accessing communication. It is estimated that the modal share of mobile phone will increase from around 64% in 2005-06 to nearly 85% in 2015-16. Due to this, mobile subscriber base will increase from 90 million in 1995-96 to more than 1150 million in 2015-16. The projected rapid growth in telephone subscriber base will have important implications for telecom operators, infrastructure providers, handset suppliers, and vendors. Telecom operators should be ready with contingency plans to deploy and operate infrastructure including customer care, billing, applications, etc., faster than that they might have initially planned. Infrastructure providers, handset suppliers, and vendors should be prepared to respond to such plans.

A New Era

A New Era

Developmental increase of total cell numbers in the murine cerebellum.

The cerebellum has been widely used as a paradigm to study basic mechanisms of brain development and cortical histogenesis. Its highly regular structure has always made it particularly attractive to approaches relying on, and yielding, quantitative information, which provide a cornerstone of systems-oriented integrative analyses. Astonishingly, though, a systematic quantification of cell generation during cerebellar development has so far not been provided. Here, we use the isotropic fractionator (i.e., cell counts based on tissue homogenates from anatomically defined regions; cf. Herculano-Houzel S, Lent R., J Neurosci. 2005;25:2518-21) to assess the developmental increase of total cell numbers in the murine cerebellum from embryonic day 17 into early adulthood. Our data show that the quantitative increase of cerebellar cell numbers follows a classical, S-shaped growth curve as described by the Hill-equation. The adult murine cerebellum was found to comprise a total of (44.03+/-0.42) * 10(6) cells, half of which are generated before postnatal day 12+/-0.18. Consistent results were obtained by using two approaches to cell counting, one based on manual assessment, the other on flow cytometry. These data provide a reliable quantitative description of cerebellar growth in the mouse and define a predictive model that should allow their integration with quantitative and qualitative descriptions of cerebellar development.

On allocation of resources during testing phase of a modular software

To provide reliable software, it is tested over a wide range of testing environment. In the process, testing resources such as time, testing personnel etc. are used. These resources are not infinitely large and therefore need to be used judiciously. In this article, we discuss the testing resource allocation problem among modules to maximize the total fault removal from software consisting of several independent components (modules). For the resulting optimization problem, we define marginal testing effort function (MTEF), where the testing resource consumption is represented in terms of fault removal. The three MTEFs proposed in this article account for both exponential and S-shaped growth curves, which are commonly used in software reliability analysis. Results are illustrated numerically using different data sets.

Mapping Quantitative Trait Loci for Longitudinal Traits in Line Crosses

Quantitative traits whose phenotypic values change over time are called longitudinal traits. Genetic analyses of longitudinal traits can be conducted using any of the following approaches: (1) treating the phenotypic values at different time points as repeated measurements of the same trait and analyzing the trait under the repeated measurements framework, (2) treating the phenotypes measured from different time points as different traits and analyzing the traits jointly on the basis of the theory of multivariate analysis, and (3) fitting a growth curve to the phenotypic values across time points and analyzing the fitted parameters of the growth trajectory under the theory of multivariate analysis. The third approach has been used in QTL mapping for longitudinal traits by fitting the data to a logistic growth trajectory. This approach applies only to the particular S-shaped growth process. In practice, a longitudinal trait may show a trajectory of any shape. We demonstrate that one can describe a longitudinal trait with orthogonal polynomials, which are sufficiently general for fitting any shaped curve. We develop a mixed-model methodology for QTL mapping of longitudinal traits and a maximum-likelihood method for parameter estimation and statistical tests. The expectation-maximization (EM) algorithm is applied to search for the maximum-likelihood estimates of parameters. The method is verified with simulated data and demonstrated with experimental data from a pseudobackcross family of Populus (poplar) trees.

Comparison of Software Reliability Assessment Methods for Open Source Software and Reliability Assessment Tool

We propose software reliability assessment methods for concurrent distributed system development by using the Analytic Hierarchy Process. Also, we make a comparison between the inflection S-shaped software reliability growth model and the other models based on a nonhomogeneous Poisson process applied to reliability assessment of the entire system composed of several software components. Moreover, we analyze software fault count data to show numerical examples of software reliability assessment for the open source project. Furthermore, we investigate an efficient software reliability assessment method for the open source system development. Also, we develop the software testing-management tool for open source software system by using Java programming language. We show several performance examples of the software testing-management tool for the open source software.

Simulation modeling of soil and plant nitrogen use in a potato cropping system in the humid and cool environment

Abstract With rising environmental concerns for current practices of fertilizer N management in the humid and cool areas, we simulated soil N dynamics and plant N use in the potato (Solanum tuberosum L.) cropping system using the software Stella. The objectives were to predict in-season N requirements by the potato crop, tuber yield, N uptake, N partitioning within root, leaf, stem and tuber, and N loss in the plant–soil system, and to examine the accuracy of using model predictions for N management in potato. The first-order linear and S-shaped growth processes were used in the simulation. The model was unidimensional and used a daily time step. Sensitivity analysis indicated that N inflow in the system was the key trait affecting potato N uptake and tuber yield. The model was validated by comparisons of the predictions with field study datasets at four sites conducted across Quebec, Canada. The simulated daily N uptake by the potato followed a S-growth pattern from the early vegetative stage to full bloom, and a plateau of N uptake appeared at late tuberization. The predicted maximum daily N uptake rate (4.46 kg ha−1 day−1) occurred at early bloom whereas the predicted maximum N transfer from stems and leaves to tubers (4.31 kg ha−1 day−1) occurred 3 weeks after the peak of N uptake. Simultaneously, high daily N uptake occurred when N concentrations in the root zone ranged between 90 and 120 kg ha−1. The predicted N uptake and potato tuber yield values were correlated to N inflows in the model (R2 = 0.91). The model estimated loss of N was 34% of the field measurements. Using model balancing the amounts of N needed by crops would lead to optimize plant growth and N use efficiency and to minimize N lost to the environment.

Complementarity and Transition to Modern Economic Growth

In developing countries, income per capita typically remains stagnant for long periods before taking-off. We study this as the outcome of a gradual transition of the workforce from traditional to modern sectors. While exogenous productivity growth is present in the modern sector only, transition to the modern sector is gradual because work experience is sector-specific and complements labor. This generates an S-shaped income growth for the dual economy, the effect of which enters into TFP in an aggregate production function. We measure the theory using nationally representative micro data from Thailand (1976-1996). The technology parameters are estimated using cross-sectional earnings equations implied by the model. We find the model simulated at these estimates captures well the nonlinear dynamics of aggregate earnings growth and inequality in Thailand.

S-shaped software reliability growth models derived from stochastic differential equations

This paper presents a software reliability growth model based on Itô type Stochastic Differential Equations (SDE). As the size of a software system becomes larger, the number of faults remaining in the system during the testing phase can be considered to be a continuous stochastic process. In practice, if the per-fault detection rate is subject to certain random effects, we may consider the use of a SDE to describe the average behavior of the software fault detection process during the testing phase. As a result, we derive several software reliability measures by utilizing the mean value function which is the expected value of the SDE. We also derive the maximum likelihood estimators of the unknown parameters for the model. Futhermore, we compare our model with other software reliability growth models in terms of several reliability measures and goodness-of-fit for the same data set.

SOFTWARE RELIABILITY GROWTH AND INNOVATION DIFFUSION MODELS: AN INTERFACE

The objective of this paper is to show an interface between modelling, allocation problems and control problems in software reliability and marketing. It has been brought out that in models which exist in software reliability and defined implicitly/explicitly for errors of two types; it is the dependency factor among errors that gives rise to S-Shaped growth curve. It is further shown that this dependency on the line of categorization of errors, adopters can be of several types/categories. Such categorization, though implicit in nature, not brought out in literature, further strengthens the fact that modeling any software phenomenon should incorporate errors of different severity rather explicitly. We have also provided a general model which can account for imperfect debugging and error generation in software reliability. The approach followed is rather implicit in nature but provides good closed form solutions. Such solutions were being alternatively looked for in innovation diffusion models namely the Bass Model, which can account for repeat purchase and growing market size. Besides we also show how problem of resource allocation and control in the two fields can be analyzed similarly. The analogy as brought out in this paper is interesting and may further lead to enriching the two areas of current research.