Search results

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.

A questionnaire is used to assess the impact of race, current past and future family income, as well as political beliefs on the support for redistribution. Current income maximization predicts those with above average income oppose redistribution. However blacks support redistribution until income is well above average and whites oppose redistribution even if income is well below average. Those with incomes below average expect to move up and this prospect of upward mobility reduces support for redistribution. The rich are more likely to espouse arguments that protect their wealth. Most intriguingly, as blacks become richer, support for redistribution falls especially rapidly.

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.

The purpose of this paper is to characterize the optimal ordering and allocation policy for a store replenishment decision in the context of an omnichannel retailer in a franchise network. The authors further show that a myopic policy is optimal, which circumvents the curse of dimensionality for the multi-period inventory model and help store managers optimize their decisions about the amount of inventory to stock for both online and offline demands and the percentage of inventory to reserve for online orders.

This research is trigged by several managerial studies which suggest reserving a certain percentage of the in-store inventory for online orders as a good store inventory allocation practice for omnichannel retailers in a franchise network. The authors used an analytical model to develop this practice by clarifying how store managers can decide on the amount of inventory to replenish and the percentage to reserve for online orders.

This study develops a finite horizon, periodic review inventory model to identify an optimal and dynamic replenishment and allocation policy. The analysis uncovers the system’s fundamental structural property concavity. The research shows that, due to this property, the optimal replenishment policy is a base-stock policy. The latter is due to the base stock level being independent of the initial inventory at hand, and the optimal allocation level being non-decreasing on the base-stock level.

This study contributes to the literature on store inventory management for omnichannel retailers in a franchise network by investigating their optimal store inventory ordering and allocation policy. Nevertheless, the zero-lead time and zero-setup cost assumptions limit the findings.

Insights into an optimal store inventory policy may guide franchisee store managers to decide on the amount of inventory to replenish and the percentage to reserve for online orders.

The originality of this paper lies in its focus on in-store inventory management for omnichannel retailers in a franchise network. The findings are helpful for franchisor retailers to implement the omnichannel strategy at the level of in-store inventory management. Beyond using incentive systems, the franchisor should leverage legitimate powers by mentioning a relevant measure in their contracts with their franchisee to minimize their channel conflicts and ensure their customers have seamless shopping experiences.

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.

Material extrusion (MEX) 3D printers suffer from an intrinsic limitation of small size of the prints due to its restricted bed dimension. On the other hand, friction stir spot welding (FSSW) is gaining wide interest from automobile, airplane, off-road equipment manufacturers and even consumer electronics. This paper aims to explore the possibility of FSSW on Acrylonitrile Butadiene Styrene/Polylactic acid 3D-printed components to overcome the bed size limitation of MEX 3D printers.

Four different tool geometries (tapered cylindrical pin with/without concavity, pinless with/without concavity) were used to produce the joints. Three critical process parameters related to FSSW (tool rotational speed, plunge depth and dwell time) and two related to 3D printing (material combination and infill percentages) were investigated and optimized using the Taguchi L27 design of experiments. The influence of each welding parameter on the shear strength was evaluated by analysis of variance.

Results revealed that the infill percentage, a 3D printing parameter, had the maximum effect on the joint strength. The joints displayed pull nugget, cross nugget and substrate failure morphologies. The outcome resulted in the joint efficiency reaching up to 100.3%, better than that obtained by other competitive processes for 3D-printed thermoplastics. The results, when applied to weld a UAV wing, showed good strength and integrity. Further, grafting the joints with nylon micro-particles was also investigated, resulting in a detrimental effect on the strength.

To the best of the authors’ knowledge, this is the first study to demonstrate that the welding of dissimilar 3D-printed thermoplastics with/without microparticles is possible by FSSW, whilst the process parameters have a considerable consequence on the bond strength.

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).

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.

The purpose of this paper is to study the sensitivity of provident fund investors to past performance and how market conditions, changes in risk and liquidity levels influence the net flows into provident funds by using a unique sample from Israel.

The study checks the impact of different levels of fund performance on provident fund flows using three alternative proxies for performance: raw return and the risk adjusted returns based on the Sharpe ratio and the Jensen’s α. The analysis relies on the time fixed effect and fund fixed effect regression models.

Results reveal that there exists an approximately concave flow–performance relationship and performance persistence among Israeli provident funds. Israeli provident fund investors are risk averse so they overreact to bad performance both in bull and bear markets. Moreover, liquidity is an important factor to influence the flow–performance curve. The investors’ strong negative response to poor performance and relative insensitivity to outperformance show that provident fund managers are not rewarded for their risk-shifting activities as in mutual funds.

The authors explore the behavior of investor flows in non-institutional retirement savings funds specifically outside of the USA, which is a topic not properly investigated in literature. Moreover, examining inflows and outflows separately gives the authors a richer understanding of investors in pension schemes. This study also enhances the understanding of the impact of fund liquidity on the flow–performance relationship for the retirement funds segment.