Theoretical Growth Model Research Articles

The Use of Size Distributions in Determining Growth Mechanisms: The Growth of Grain Boundary Precipitates in Cobalt-20 Iron

Accurate prediction of microstructural stability in an alloy depends not only on a sound knowledge of the thermodynamics of the system but also of the kinetics of the phase changes involved. Conventionally, precipitate growth mechanisms have been inferred from the variation with aging time of various single parameters such as the mean, mode or maximum of the precipitate size distribution, which has then been compared to theoretical models of growth of an individual precipitate. In the present study, the development, with aging time at 1003 K (730 °C), of the size and shape distributions of grain boundary precipitates in Co-20Fe has been examined to determine the rate-controlling processes, and the conclusions compared to those from conventional analysis. The growth of the precipitates was well described by the grain boundary-dependent collector plate mechanism of Brailsford and Aaron. As the precipitates grew, low-energy facets were formed, which could move only by the propagation of ledges, and thickening was inhibited. The precipitates’ diffusion fields in the grain boundary overlapped and the size distributions of the longest aged specimens showed that local coarsening occurred under partial interface control.

Electrification and productivity growth in Korean manufacturing plants

This paper presents a theoretical model of firm-specific productivity growth that incorporates technological knowledge by electrification and tests the model empirically. Our theoretical explanations suggest that the energy-transformation from fossil fuel to electricity by electrification could cause a decrease in the short-term level of productivity but an increase in the long-term rate of productivity growth in firms. Our empirical evidence from a large panel of Korean manufacturing plants is generally consistent with the theoretical predictions on the relatedness of technological knowledge by the electrification to the level and rate effects of the firm's productivity. The electrification measured by the share of electricity results in lowering the short-term productivity level but in raising the long-term rate of productivity growth of firms.

In-situ HRTEM observations of growth process of decagonal quasicrystals

Quasicrystals possess quasiperiodicity, where the structure cannot be described simply by the repetition of unit cell like conventional crystals. This fact raises the question of how quasicrystals grow, i.e., what physical mechanism makes the growth of quasicrystals possible. While crystals can grow by copying a unit cell via local atomic interactions, nonlocal structural information seems to be required in the growth of quasicrystals. This problem has attracted much attention ever since the first discovery of a quasicrystal in 1984, and several theoretical growth models [1] have been proposed. However, no experimental studies have so far been reported, and it is still unclear whether these theoretical growth models apply to real quasicrystals. In the present study, we have conducted in-situ high-temperature electron microscopic (HRTEM: High-Resolution Transmission Electron Microscopy) observations of the growth process of decagonal quasicrystals to elucidate the growth mechanism. The growth processes of a decagonal quasicrystal of Al70.8Ni19.7Co9.5were observed by HRTEM in the temperature range 1073-1173K. Tiling patterns with edge length of about 2nm were constructed from a series of HRTEM images. They were analysed in the framework of the projection method. Here, we followed the procedures in our previous work [2]. We have already reported the results of some observations and analyses elsewhere [3]. However, the growth processes of them were on a small scale, and the results were indefinite. Recently, we have succeeded in observing a growth process on a massive scale. In this paper, we present the results of this observation and subsequent analyses, and discuss the growth mechanism of the quasicrystal.

DISCONTINUITY OF OUTPUT CONVERGENCE WITHIN THE UNITED STATES: WHY HAS THE COURSE CHANGED?

Has the progress of output convergence changed within the United States? This article examines the output convergence among U.S. states for the last five decades by making several improvements over the extant literature. By applying a battery of convergence tests designed to capture nonlinear transitional dynamics to real output per worker data (i.e., nominal values deflated by state‐level price), we find that output convergence has not been a feature of the continental United States since the 1970s. Instead, output convergence has proceeded among four subgroups within which constituent states have certain characteristics in common. Our regression analysis suggests that state‐level characteristics related to technology and human capital play a crucial role in accounting for the formation and composition of convergence clubs, in agreement with the recent theoretical models of growth and development (e.g., Aghion et al. 2009; Gennaioli et al. 2013b). The level of technology, proxied by patents, turns out to be a consistently significant determinant even after controlling for endogeneity, suggesting that frictions in the diffusion of technology and human capital may have led to clustering of states with different levels of productivity. Our results therefore cast doubt on the common view that diffusion of knowledge and technology across state borders is frictionless. (JEL O47, O51)

El rol de la salud en el proceso de crecimiento económico: una revisión de la literatura.

We perform an analysis of the consideration in the literature about health as determinant of economic growth. The existing contributions fall into three approaches. On the one hand, theoretical models of growth where health status is incorporated as key factor in the growth process. On the other hand, growth accounting models which consider the contribution of each production factor, among which includes health status, to changes in income. Finally, third approach is based on a la Barro regressions, which returns the rate of growth over wide range of variables, which include the health status.

Smart endogenous growth: cultural capital and the creative use of skills

Purpose – Despite the growing literature aimed at explaining how cultural and artistic production feeds economic growth, the causal relationships and interplays are not investigated in depth. In the attempt of filling this gap, the purpose of this paper is to examine arts, culture, and education within the framework of the New Growth Theory. Design/methodology/approach – Starting from the analysis of how culture may be at the root of a specific engine of economic growth, the paper presents a theoretical endogenous growth model driven by the combination of the investments in human and cultural capital. Findings – The paper shows that cultural investment has a positive impact on economic growth and on the level of income provided that the economy is sufficiently “culture-intensive”, and that this effect is further magnified the more total factor productivity (TFP) is sensitive to the stock of cultural capital. Research limitations/implications – The paper figures out the possibility of a cultural poverty tr...

Drug pricing and control of health expenditures: a comparison between a proportional decision rule and a cost-per-QALY rule.

In Germany, the Institute for Quality and Efficiency in Health Care (IQWiG) makes recommendations for reimbursement prices of drugs on the basis of a proportional relationship between costs and health benefits. This paper analyzed the potential of IQWiG's decision rule to control health expenditures and used a cost-per-quality-adjusted life year (QALY) rule as a comparison. A literature search was conducted, and a theoretical model of health expenditure growth was built. The literature search shows that the median incremental cost-effectiveness ratio of German cost-effectiveness analyses was €7650 per QALY gained, thus yielding a much lower threshold cost-effectiveness ratio for IQWiG's rule than an absolute rule at €30 000 per QALY. The theoretical model shows that IQWiG's rule is able to contain the long-term growth of health expenditures under the conservative assumption that future health increases at a constant absolute rate and that the threshold incremental cost-effectiveness ratio increases at a smaller rate than health expenditures. In contrast, an absolute rule offers the potential for manufacturers to raise drug prices in response to the threshold, thus resulting in an initial spike in expenditures. Results suggest that IQWiG's proportional rule will lead to lower drug prices and a slower growth of health expenditures than an absolute cost-effectiveness threshold at €30 000 per QALY. This finding is surprising as IQWiG's rule-in contrast to a cost-per-QALY rule-does not start from a fixed budget.

A theoretical model of semi-elliptic surface crack growth

A theoretical model of semi-elliptic surface crack growth based on the low cycle strain damage accumulation near the crack tip along the cracking direction and the Newman–Raju formula is developed. The crack is regarded as a sharp notch with a small curvature radius and the process zone is assumed to be the size of cyclic plastic zone. The modified Hutchinson, Rice and Rosengren (HRR) formulations are used in the presented study. Assuming that the shape of surface crack front is controlled by two critical points: the deepest point and the surface point. The theoretical model is applied to semi-elliptic surface cracked Al 7075-T6 alloy plate under cyclic loading, and five different initial crack shapes are discussed in present study. Good agreement between experimental and theoretical results is obtained.

Knowledge Growth Measurement and Formulation for Enhancing Organizational Knowledge Capital

This paper offers a conceptual framework for those details with the main component features for modeling knowledge growth. It has been contributing to important insights to future studies in the field of knowledge management to design a theoretical and operational model of knowledge growth in enhancing organizations’ knowledge capital. This study approach considers three important issues: such as the categories of knowledge for measurement, the elicitation and measurement of organizational knowledge growth by designing a knowledge growth elicitation and measurement tool (KGEMT), and formulating a model for knowledge growth measurement. The review and analyses show that knowledge growth measurement and elicitation is an active research spanning from the concepts that include the stages of knowledge growth; evolutionary theories that involve continuous organizational learning; knowledge growth elicitation to capture the component features of a knowledge growth process from users formulation of knowledge growth; and formation of knowledge capital. From these findings, the study conceptualized a framework for modeling and measuring organizational knowledge growth. The study developed the knowledge elicitation and measurement tool, which captures work episodes of knowledge workers in organizations; organizing the knowledge into explicit and tacit knowledge, and enumerating such knowledge to produce a measure of knowledge growth within the duration of measurement. While the results of the enumeration may be subject to criticism, the tool does provide an indication of the knowledge growth in organizations.

A theoretical basis for green growth

This paper proposes a theoretical model of green growth. The paper analyses the development mechanisms through which natural resource capital regenerates (or at least does not degrade), is preserved and contributes to economic growth. Climate change is a threat to human civilisation and countries need to save natural resources, which are a crucial form of productive capital in the economy, and also challenge economic development in the 21st century. One of the new development strategies proposed is green growth which leads towards sustainable development. This paper suggests policy inputs regarding the regeneration of natural resources and their preservation in terms of watershed development, flood control and development of ecosystem services through the creation of jobs through the channel of productive consumption. Policy-makers should focus on employability, regeneration and preservation of natural resource capital for sustaining livelihoods in the economy.

Growth of Mushy Zone during Two-dimensional Solidification with Supercooling （Theoretical model for selective growth of primary dendrite arms）

Growth of Mushy Zone during Two-dimensional Solidification with Supercooling （Theoretical model for selective growth of primary dendrite arms）

Controlling mechanisms in directional growth of aggregated archaeal cells.

Members of the family Methanosarcinaceae are important archaeal representatives due to their broad functionality, ubiquitous presence, and functionality in harsh environments. A key characteristic is their multicellular (packet) morphology represented by aggregates of spatially confined cells. This morphology is driven by directed growth of cells in confinement with sequential variation in growth direction. To further understand why spatially confined Methanosarcina cells (and in general, confined prokaryotes) change their direction of growth during consecutive growth-division stages, and how a particular cell senses its wall topology and responds to changes on it a theoretical model for stress dependent growth of aggregated archaeal cells was developed. The model utilizes a confined elastic shell representation of aggregated archaeal cell and is derived based on a work-energy principle. The growth law takes into account the fine structure of archaeal cell wall, polymeric nature of methanochondroitin layer, molecular-biochemical processes and is based on thermodynamic laws. The developed model has been applied to three typical configurations of aggregated cell in 3D. The developed model predicted a geometry response with delayed growth of aggregated archaeal cells explained from mechanistic principles, as well as continuous changes in direction of growth during the consecutive growth-division stages. This means that cell wall topology sensing and growth anisotropy can be predicted using simple cellular mechanisms without the need for dedicated cellular machinery.

Cellular growth of single-phase Zn–Ag alloys unidirectionally solidified

Transient unidirectional solidification experiments have been carried out with a single-phase Zn–Ag alloy under cooling rates in the range of 0.1–40 K s−1. The resulting macrostructure is shown to be typified by columnar grains aligned along the heat flow direction and the microstructure is characterized by a cellular morphology along the entire casting length with no evidence of cellular/dendritic transition. A regular to plate-like cells transition is shown to occur for cooling rates higher than 10K s−1. Experimental results from the literature on the cellular growth of single-phase Zn–Ag alloys in steady-state solidification conditions are compared with the results of the present investigation. An experimental growth law relating the cell spacing with the cooling rate is proposed, which is shown to be able to represent both the steady-state and transient growth regimes of single-phase Zn–Ag alloys. The Bouchard–Kirkaldy model is shown to be the only theoretical growth model that matches the cellular experimental scatters in both solidification regimes.

Public debt and the limits of fiscal policy to increase economic growth

This study proposes a theoretical model of endogenous growth that demonstrates that the level of the public debt-to-gross domestic product (GDP) ratio should negatively impact the effect of fiscal policy on growth. This effect occurs because government indebtedness extracts a portion of young people's savings to pay interest on the debts. Therefore, the payment of debt interest requires an allocation exchange system across generations that is similar to a pay-as-you-go pension system, which results in changes in the savings rate of the economy. The major conclusions of the theoretical model were verified using an econometric model that provides evidence of the validity of this conclusion. Our empirical analysis controls for time-invariant, country-specific heterogeneity in growth rates. We also address endogeneity issues and allow for heterogeneity across countries in the model parameters and for cross-sectional dependence.

Prediction of fatigue crack growth based on low cycle fatigue properties

Theoretical models of the fatigue crack growth without artificial adjustable parameters were proposed by considering the plastic strain energy and the linear damage accumulation, respectively. The crack was regarded as a sharp notch with a small curvature radius and the process zone was assumed to be the size of cyclic plastic zone. The near crack tip elastic–plastic stress and strain were evaluated in terms of modified Hutchinson, Rice and Rosengren (HRR) formulations. Predicted results from two established models have been soundly compared with open reports for frequently used materials. It is found that experimental results agree well with theoretical solutions.

Does the neoclassical growth model predict interregional convergence? On the impact of free factor movement and the implications for the European Union

This paper sets up a theoretical model of regional growth with free factor movement. The analysis shows that factor endowments are crucial for a region’s attractiveness regarding factor relocations. In particular, lower endowments of human capital within other regions are advantageous for a region’s growth prospects, and vice versa. The paper concludes that under the framework of free factor movement, the European Union’s objective of interregional convergence can only be achieved by subsidising disadvantaged economies.

Quality and endogenous tourism: An empirical approach

We propose a theoretical model and an empirical study that highlight the role of quality of tourism services and endogenous tourism in long-run economic growth. We study a theoretical growth model of international trade where tourism is the growth engine and quality of tourism services has a positive impact on long-term growth. We also provide an empirical analysis to test the relation between tourism, quality and economic growth in Spain over the period 1970–2010. Our results show that in the long run, tourist arrivals, quality of tourism accommodations, and foreign GDP have a positive effect on Spanish GDP. In the short term, changes in economic growth appear to lead to growth in tourist arrivals. Our findings support a two-way causal relationship between real GDP growth and tourism growth in Spain.

Spatial Spillovers and the Convergence of Regional Economic Growth: A Case Study Based on the Yangtze River Delta∗

Spatial club convergence means that the economic growth of a group of regions that have similar initial conditions and structural characteristics and are spatially adjacent will gradually converge on the same steady state. As a new field in research on the club convergence of regional economic growth, spatial club convergence works on a mechanism whereby spatial spillovers drive the localized growth of the regional economy, leading to spatial club convergence. Using a theoretical model of regional economic growth that includes spatial spillovers, this study shows that these spillovers can lead to spatial club convergence. Our empirical analysis of regional economic growth in the Yangtze River Delta in 1990-2007 also shows that spatial spillovers can affect regional economic growth, and that spatial club convergence does exist. When the spatial spillover factor is taken into account, the speed of spatial club convergence in the Yangtze River Delta is 1.57 percent.

Aging logarithmic Galilean field theories

We analytically compute correlation and response functions of scalar operators for the systems with Galilean and corresponding aging symmetries for general spatial dimensions d and dynamical exponent z, along with their logarithmic and logarithmic squared extensions, using the gauge/gravity duality. These non-conformal extensions of the aging geometry are marked by two dimensionful parameters, eigenvalue M of an internal coordinate and aging parameter α.We further perform systematic investigations on two-time response functions for general d and z, and identify the growth exponent as a function of the scaling dimensions Δ of the dual field theory operators and aging parameter α in our theory. The initial growth exponent is only controlled by Δ, while its late time behavior by α as well as Δ. These behaviors are separated by a time scale order of the waiting time. We attempt to make contact our results with some field theoretical growth models, such as Kim–Kosterlitz model at higher number of spatial dimensions d.

Top Marginal Taxation and Economic Growth

The paper explores the relationship between statutory top marginal tax rates on personal income and long‐run economic growth. While theoretical models of endogenous growth explicitly allow for nonlinear effects of taxation on economic growth, the majority of existing empirical studies assume a linear association. By contrast, this paper investigates both a linear and a non‐monotonic relationship between top tax rates and GDP growth. Using a panel of 18 OECD countries over the period 1960‐2009, this paper finds support in favor of a quadratic top tax‐growth relationship. Results are robust to different model specifications and estimation techniques. The point estimates of the regressions suggest that the marginal effect of higher top tax rates becomes negative above a growth maximizing tax rate on the order of 60 percent. The quadratic relationship found for the whole sample period does not hold over the period 1975‐2009. Instead, the link between top tax rates and GDP growth after 1975 is well summarized by a linear and positive top tax‐growth relationship. Since, top marginal tax rates after 1975 are often below the estimated growth maximizing level, such a result suggest that the top tax‐growth relationship after 1975 might be placed on the upward‐sloping side of the “growth‐hill”. There is an even stronger positive top tax‐growth relationship after 1985, when average top tax rates across OECD are lower than 50%.