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The purpose of this paper is to find a new logarithmic profile model of cylindrical roller bearing, which is expected to avoid edge effect and allow a straight portion on the roller considering uniform pressure distribution and easier manufacturing.

A new logarithmic cylindrical roller profile model using three parameters is proposed. Contact model between roller and rings and quasi-static model of roller bearing are given to obtain contact pressure distribution and solved by multi-grid and Newton–Raphson method. Optimization of modified reference rating life model of the roller bearing is proposed by using genetic algorithms.

Under heavy load or tilting moment conditions, modified reference rating life of cylindrical roller bearing may increase greatly by optimization of three design parameters using the new logarithmic profile model.

The results of the present paper could aid in the design of logarithmic profile of cylindrical roller bearing and increase fatigue life of cylindrical roller bearing.

We propose a methodology for estimating preference parameters in matching models. Our estimator applies to repeated observations of matchings among a fixed group of individuals. Our estimator is based on the stability conditions in matching models; we consider both transferable (TU) and nontransferable utility (NTU) models. In both cases, the stability conditions yield moment inequalities which can be taken to the data. The preference parameters are partially identified. We consider simple illustrative examples, and also an empirical application to aggregate marriage markets.

This paper aims to examine the impact of key affective moments of a playful experience on consumers’ overall retrospective evaluations.

The authors build on past literature on hedonic psychology and sequential preferences and link it to specific characteristics of playful experiences to derive their hypotheses. The hypotheses are tested through two field experiments conducted at a videogame arcade.

Results demonstrated that consumers’ overall evaluations are better aligned with the affective intensity at the final or end moment of a playful experience. Findings also revealed the complexity of understanding playful experiences, for it is the meaningfulness of end moments rather than simply their recent position in the experience that underlies overall evaluations. When end moments cease to be meaningful, the trough or least affective intense moment impacts overall evaluations.

This research has implications for marketers who are deciding on which point of a playful experience to concentrate their resources for optimizing evaluations.

This research contributes to literature on playful consumption by illuminating how consumers rely on affective moments of a playful experience to construct overall evaluations. Additionally, it highlights the important role of meaningfulness of end moments, a relatively underexplored process, which extends literature on key moments and retrospective evaluations.

The purpose of this paper is to propose that conceptions of time and future that are currently in use restrict the possibilities for framing decision making. By privileging the notion of present moment over that of linear time, a more comprehensive framing of what it means to consider what influences our judgements. The ontology of the present moment provides a theoretical context for knowing what we can of the future in a more comprehensive way.

A review of ways of knowing the future that extends beyond linear assumptions of time leads to consideration of anticipatory systems and of the relationship between purpose and causality. It leads further into conjecture that the present moment is more ontologically fundamental than what we customarily refer to as past, present and future.

On this foundation, examination of experience of now reveals a multidimensionality which can include retrocausality, the possibility of the future influencing the present and the importance of latent patterning in determining events.

The notion of the present moment has much in common with second order cybernetics and indicates a possible way of bringing systems thinking, especially boundary critique, to futures thinking and strategic decision making.

Although basically a theoretical paper, the framework does suggest possibilities for redesigning futures practice through using the present moment as a meta‐framing critique technique to reveal more clearly underlying assumptions in both futures studies and systems thinking.

In the context of a world where serious inability to see what is coming is pervasive in management and governance, a fresh look at fundamental assumptions may reveal flawed decision thinking and indicate ways of improvement.

The purpose of this paper is to address the practically important problem of the load dependence of transverse vibrations for helical springs. At the beginning, the author develops the equations for transverse vibrations of the axially loaded helical springs. The method is based on the concept of an equivalent column. Second, the author reveals the effect of axial load on the fundamental frequency of transverse vibrations and derive the explicit formulas for this frequency. The fundamental natural frequency of the transverse vibrations of the spring depends on the variable length of the spring. The reduction of frequency with the load is demonstrated. Finally, when the frequency nullifies, the side buckling spring occurs.

Helical springs constitute an integral part of many mechanical systems. A coil spring is a special form of spatially curved column. The center of each cross-section is located on a helix. The helix is a curve that winds around with a constant slope of the surface of a cylinder. An exact stability analysis based on the theory of spatially curved bars is complicated and difficult for further applications. Hence, in most engineering applications a concept of an equivalent column is introduced. The spring is substituted for the simplification of the basic equations by an equivalent column. Such a column must account for compressibility of axis and shear effects. The transverse vibration is represented by a differential equation of fourth order in place and second order in time. The solution of the undamped model equation could be obtained by separation of variables. The fundamental natural frequency of the transverse vibrations depends on the current length of the spring. Natural frequency is the function of the deflection and slenderness ratio. Is the fundamental natural frequency of transverse oscillations nullifies, the lateral buckling of the spring with the natural form occurs. The mode shape corresponds to the buckling of the spring with moment-free, simply supported ends. The mode corresponds to the buckling of the spring with clamped ends. The author finds the critical spring compression.

Buckling refers to the loss of stability up to the sudden and violent failure of seed straight bars or beams under the action of pressure forces, whose line of action is the column axis. The known results for the buckling of axially overloaded coil springs were found using the static stability criterion. The author uses an alternative approach method for studying the stability of the spring. This method is based on dynamic equations. In this paper, the author derives the equations for transverse vibrations of the pressure-loaded coil springs. The fundamental natural frequency of the transverse vibrations of the column is proved to be the certain function of the axial force, as well as the variable length of the spring. Is the fundamental natural frequency of transverse oscillations turns to be to zero, is the lateral buckling of the spring occurs.

The spring is substituted for the simplification of the basic equations by an equivalent column. Such a column must account for compressibility of axis and shear effects. The more accurate model is based on the equations of motion of loaded helical Timoshenko beams. The dimensionless for beams of circular cross-section and the number of parameters governing the problem is reduced to four (helix angle, helix index, Poisson coefficient, and axial strain) is to be derived. Unfortunately, that for the spatial beam models only numerical results could be obtained.

The closed form analytical formulas for fundamental natural frequency of the transverse vibrations of the column as function of the axial force, as well as the variable length of the spring are derived. The practically important formulas for lateral buckling of the spring are obtained.

In this paper, the author derives the new equations for transverse vibrations of the pressure-loaded coil springs. The author demonstrates that the fundamental natural frequency of the transverse vibrations of the column is the function of the axial force. For study of the stability of the spring the author uses an alternative approach method. This method is based on dynamic equations. The new, original expressions for lateral buckling of the spring are also obtained.

This study aims to examine the effects of institutions on private investment (PI) using panel data analysis, where the sample countries consist of 100 countries around the world and the time period is covering from 2007 to 2016. The system generalized method of moments (GMM) estimator, introduced by Arellano and Bond (1991) and further developed by Blundell and Bond (1998) is used to analyze the data sets.

This study uses the panel data approach to estimate the empirical model due to the panel nature of the data. In particular, due to the presence of lagged dependent variables and the ability to capture individual country-specific effects, the system GMM estimator, introduced by Arellano and Bond (1991) and further developed by Blundell and Bond (1998), is adopted to analyze the roles of institutions in PI. The system GMM is developed specifically to solve the problems of weak instruments and persistency (Blundell and Bond, 1998). Jointly, they suggest to adopt additional moment conditions where lagged difference of the dependent variable is orthogonal to the level form of the disturbances. The system GMM estimator is able to combine the moment conditions for the different models, as well as the level model, thereby (is capable of) generate consistent and efficient parameters. Due to the dynamic nature of the data, this study uses one-step and two-step system GMM to investigate the roles of institutions in PI.

The empirical results based on the two-step system GMM demonstrate that the quality of institutions plays an important role in stimulating PI. The finding is reinforced by the analysis of the institutional sub-components’ effects on PI.

This study is unique as its measurement of institutions is multi-dimensional (including law and order, rules and regulation, government stability, bureaucratic quality, control of corruption, socio-economic condition, etc.), and hence are more comprehensive. Second, it is different than the previous studies as its sample of countries includes both democracies and non-democracies, as well as both developed and non-developed economies in which policy implications are widely acceptable. Third, this study contributes to the policymakers especially those in the debt-ridden economies where governments are budget-tightening (limited capacity for public investment), as to which practical direction should be focused on so as to attract PI and eventually sustainable growth can take place.

The authors propose a new frequentist approach to sign restrictions in structural vector autoregressive models. By making efficient use of non-Gaussianity in the data, point identification is achieved which facilitates standard asymptotic inference and, hence, the assessment of theoretically implied signs and labelling of the statistically identified structural shocks. The authors illustrate the benefits of their approach in an empirical application to the US labour market.

This chapter analyzes the properties of an alternative least-squares based estimator for linear panel data models with general predetermined regressors. This approach uses backward means of regressors to approximate individual specific fixed effects (FE). The author analyzes sufficient conditions for this estimator to be asymptotically efficient, and argue that, in comparison with the FE estimator, the use of backward means leads to a non-trivial bias-variance tradeoff. The author complements theoretical analysis with an extensive Monte Carlo study, where the author finds that some of the currently available results for restricted AR(1) model cannot be easily generalized, and should be extrapolated with caution.

This chapter reviews the recent developments in the estimation of panel data models in which some variables are only partially observed. Specifically we consider the issues of censoring, sample selection, attrition, missing data, and measurement error in panel data models. Although most of these issues, except attrition, occur in cross-sectional or time series data as well, panel data models introduce some particular challenges due to the presence of persistent individual effects. The past two decades have seen many stimulating developments in the econometric and statistical methods dealing with these problems. This review focuses on two strands of research of the rapidly growing literature on semiparametric and nonparametric methods for panel data models: (i) estimation of panel models with discrete or limited dependent variables and (ii) estimation of panel models based on nonparametric deconvolution methods.

The purpose of this study is to examine the interactive role of human capital development (HCD) in foreign aid-growth relations in South Asia and sub-Saharan Africa countries from 1985–2019.

The study used panel data that cut across all countries in South Asia and sub-Saharan Africa collected from The World Bank’s Development Indicators. The data were analysed using Bai and Ng panel unit root idiosyncratic cross-sectional tests and the system generalised method of moments (SGMM).

The study found that foreign aid and HCD have negative impacts on economic growth. Fortunately, the interaction of human capital with foreign aid reduces the extent to which foreign aid impedes economic growth. The presumption is that South Asia and sub-Saharan Africa economies had not reaped the potential growth effect of foreign aid inflows due to high illiteracy rates and weak social capacities. The peculiarity of these regions hinders the absorptive capacity to transform positive externality associated with foreign aid into sizeable economic prosperity.

It is imperative for South Asia and sub-Saharan Africa countries to not depend on foreign aid; instead, the strategic action by policymakers should be to developing sustainable social capacities with HCD as the centre-piece.

The highpoint of this study is its inter-regional approach and the interplay between human capital and foreign aid using the second generation panel unit root estimator and the SGMM approaches.