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The purpose of this paper is to investigate the effects of concavity level on performance parameters of a parabolic fin under the influences of natural convection and radiation.

Computational fluid dynamics software (FLUENT) is used for the heat transfer analysis. Optimum fin geometry is searched in order to maximize the heat dissipation from fin to the ambient while minimizing the volume of fin.

The fin profile with concavity level of 2 dissipates 14.92, 17.53, 24.33 and 26.60 percent more heat and uses 34.62, 49.64, 57.66 and 63.09 percent much material compared to the fin with concavity level of 4, 6, 8 and 10, respectively. It is also observed that the amount of heat dissipation per mass considerably increases with increasing concaveness.

The research was carried out for five different concavity levels in the range of 2-10.

The results can be used in passive cooling applications of PV systems. Also, heat sinks for CPU cooling can be redesigned with respect to the results obtained from the research.

In this paper, effects of concavity level on performance parameters of a parabolic fin are investigated for the first time. It is observed from the numerical results that the fin profile with higher concavity levels provides a cheaper and lighter heat dissipation device so it is recommended for the applications where the weight and the cost are primary considerations such as cooling of photovoltaics.

Economic conditions such as convexity, homogeneity, homotheticity, and monotonicity are all important assumptions or consequences of assumptions of economic functionals to be estimated. Recent research has seen a renewed interest in imposing constraints in nonparametric regression. We survey the available methods in the literature, discuss the challenges that present themselves when empirically implementing these methods, and extend an existing method to handle general nonlinear constraints. A heuristic discussion on the empirical implementation for methods that use sequential quadratic programming is provided for the reader, and simulated and empirical evidence on the distinction between constrained and unconstrained nonparametric regression surfaces is covered.

The purpose of this paper is to answer the question of workforce diversity and efficiency. It departs from the rather ad hoc approach used in most recent empirical papers exploiting firm-level evidence, and suggests focusing on the estimation of the degree of concavity of the production function.

Workforce diversity is optimal when the technology displays concavity in the share of workers considered (e.g. decreasing marginal contribution of rising shares of more productive/skilled workers). What is also shown in this paper is that a generalised version of the production function à-la-Hellerstein-Neumark (HN) – where workforce diversity is captured via an index of labour shares – is suitable for estimating the concavity of the technology, and thus for assessing the case for/against workforce diversity.

The paper contains an application to two panels of Belgian firms covering the 1998-2012 period. The main empirical result is that of an absence of strong evidence that age, gender or educational diversity is good or bad for efficiency.

The key idea of the paper is that the degree of convacity/convexity in the share of workers considered of firm-level technology and the desirability/efficiency of workforce diversity are intrinsically connected. It is also that a non-linear/CES version of the HN labour-quality index can be used in empirical work to assess the degree of concavity/convexity of the technology and quantify the efficiency gains/losses of workforce diversity.

Shaft orbit is an important characteristic for vibration monitoring and diagnosing system of hydroelectric generating set. Because of the low accuracy and poor reliability of traditional methods in identifying the shaft orbit moving direction (MD), the purpose of this paper is to present a novel automatic identification method based on trigonometric function and polygon vector (TFPV).

First, some points on shaft orbit were selected with inter‐period acquisition method and joined together orderly to form a complex plane polygon. Second, by using the coordinate transformation and rotation theory, TFPV were applied comprehensively to judge the concavity or convexity of the polygon vertices. Finally, the shaft orbit MD is identified.

The simulation and experiment demonstrate that the method proposed can effectively identify the common shaft orbit MD.

In order to identity the shaft orbit MD effectively, a novel automatic identification method based on TFPV is proposed in this paper. The problem of identifying the shaft orbit MD is transformed into the problem about orientation of complex polygons, which are formed orderly by points on orbit shaft, and TFPV are applied comprehensively to judge the concavity or convexity of the polygon vertices.

This study aims to carry out the analysis of Rayleigh-Bénard convection within enclosures with curved isothermal walls, with the special implication on the heat flow visualization via the heatline approach.

The Galerkin finite element method has been used to obtain the numerical solutions in terms of the streamlines (ψ ), heatlines (Π), isotherms (θ), local and average Nusselt number ( Nut¯) for various Rayleigh numbers (10³ ≤ Ra ≥ 10⁵), Prandtl numbers (Pr = 0.015 and 7.2) and wall curvatures (concavity/convexity).

The presence of the larger fluid velocity within the curved cavities resulted in the larger heat transfer rates and thermal mixing compared to the square cavity. Case 3 (high concavity) exhibits the largest Nut¯ at the low Ra for all Pr. At the high Ra, Nut¯ is the largest for Case 3 (high concavity) at Pr = 0.015, whereas at Pr = 7.2, Nut¯ is the largest for Case 1 (high concavity and convexity).

The results may be useful for the material processing applications.

The study of Rayleigh-Bénard convection in cavities with the curved isothermal walls is not carried out till date. The heatline approach is used for the heat flow visualization during Rayleigh-Benard convection within the curved walled enclosures for the first time. Also, the existence of the enhanced fluid and heat circulation cells within the curved walled cavities during Rayleigh-Benard heating is illustrated for the first time.

This paper aims to study the impact of convexity and concavity of the vertical borders on double-diffusive mixed convection. In addition, the study of entropy generation is performed. This numerical study has been carried out for different patterns of wavy edges to reveal their effects on heat and mass transfer phenomena.

Four different flow features are treated by varying the directions of convexity and concavity of the vertical walls. A uniform temperature, as well as concentration distributions, are introduced to the left border while keeping a cold temperature and low concentration for the right border. The horizontal boundaries are in adiabatic condition. The upper border of the chamber is moving in the right direction with an equal speed. The governing Navies–Stokes equations are designed to describe energy and species transport phenomena, and these equations are solved by compact scheme.

The investigated results are analyzed for various parameters, namely, Prandtl number, Richardson number, thermal Grashof number, Lewis number, Buoyancy ratio and amplitude of the wavy walls. It is observed that the thermal and solutal transfer performance becomes effective with lower Richardson numbers. The results reveal that the concavity and convexity of the side borders of the cabinet can control the thermosolutal performance. It is also observed that among all wavy chambers, Case-4 records maximum thermosolutal transfer rate, while Case-3 attains minimum thermosolutal transfer rate.

This work is an example of solar thermal power conversion, power collection systems, systems of energy deficiency, etc.

Much of the literature on theories of decision making under risk has emphasized differences between theories. One enduring theme has been the attempt to develop a distinction between “normative” and “descriptive” theories of choice. Bernoulli (1738) introduced log utility because expected value theory was alleged to have descriptively incorrect predictions for behavior in St. Petersburg games. Much later, Kahneman and Tversky (1979) introduced prospect theory because of the alleged descriptive failure of expected utility (EU) theory (von Neumann & Morgenstern, 1947).

We present the results of a questionnaire study with Belgian undergraduate students as respondents. We consider the relationship between people’s direct ethical preferences, their preferences behind a veil of ignorance, and their purely individual risk preferences over income distributions. The results reveal that, although there are important similarities between the three types of preferences, the first and third types form two extremes, while the second type lies in between the other two. Consistency of response patterns with the expected utility (EU) and rank-dependent expected utility (RDEU) models – natural analogues of the social welfare functions most frequently used in the literature on inequality and social welfare – is tested as well. For all three types of preferences the results reveal that, in the considered context, the RDEU model does not add explanatory power to the EU model. However, preferences appear to be relatively well described by some of the basic concepts from non-expected utility theory not usually considered in the income distribution literature.