Effect of cavity surface coating and molding parameters on pressure drop: Developing a new software for rapid calculations

Nowadays, many of the plastic components are aesthetic pieces, and they are fabric, thermoplastic vulcanizates (TPVs), or film coated. In the case of upholstered pieces, they are injected onto a textile tissue introduced into the mold, and they are finished with an edging process. Simulation programs used to optimize the injection process are not able to simulate the injection over fabrics, and therefore, it is difficult to select an injection machine without knowing the pressure drop inside the mold and without knowing how the parameters affect to the injection cycle or to the aesthetic aspect of this kind of pieces. This article presents a software for rapid calculations during the filling phase without the need for complex modeling. The program will be able to calculate pressure drop and other flow parameters that are fundamental for a good design of an industrial mold used in in‐mold decoration (IMD) technique. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Evaluating content quality and helpfulness of online product reviews: The interplay of review helpfulness vs. review content

Online reviews have received much attention recently in the literature, as their visibility has been proven to play an important role during the purchase process. Furthermore, recent theoretical insight argue that the votes casted on how helpful an online review is (review helpfulness) are of particular importance, since they constitute a focal point for examining consumer decision making during the purchase process. In this paper, we explore the interplay between online review helpfulness, rating score and the qualitative characteristics of the review text as measured by readability tests. We construct a theoretical model based on three elements: conformity, understandability and expressiveness and we investigate the directional relationship between the qualitative characteristics of the review text, review helpfulness and the impact of review helpfulness on the review score. Furthermore, we examine whether this relation holds for extreme and moderate review scores. To validate this model we applied four basic readability measures to a dataset containing 37,221 reviews collected from Amazon UK, in order to determine the relationship between the percentage of helpful votes awarded to a review and the review text’s stylistic elements. We also investigated the interrelationships between extremely helpful and unhelpful reviews, as well as absolutely positive and negative reviews using intergroup comparisons. We found that review readability had a greater effect on the helpfulness ratio of a review than its length; in addition, extremely helpful reviews received a higher score than those considered less helpful. The present study contributes to the ever growing literature on on-line reviews by showing that readability tests demonstrate a directional relationship with average length reviews and their helpfulness and that this relationship holds both for moderate and extreme review scores.     

Deforming Time in a Nonadditive Discount Function

The aim of this paper is to present a methodology to generate a partially subadditive (respectively superadditive) discount function starting from an entirely subadditive (respectively superadditive) discount model. To do this, we are going to use the concept of deformation of time in a discount function, focusing on Stevens' power law. A deformation of time is a function that mathematically represents the perception from an individual or a group of individuals about how the calendar time evolves. This approach will be important when describing the treatment of addictions and other diseases in patients who show a certain degree of impulsivity in their intertemporal choice.     

Using OR to adapt supply chain management best practices to humanitarian logistics

The demand for humanitarian aid is extraordinarily large and it is increasing. In contrast, the funding for humanitarian operations does not seem to be increasing at the same rate. Humanitarian logistics has the challenge of allocating scarce resources to complex operations in an efficient way. After acquiring sufficient contextual knowledge, academics can use operations research (OR) to adapt successful supply chain management best practices to humanitarian logistics. We present two cases of OR applications to field vehicle fleet management in humanitarian operations. Our research shows that by using OR to adapt supply chain best practices to humanitarian logistics, significant improvements can be achieved.     

Influence of texture and test velocity on the dynamic,high-strain,tensile behavior of zirconium

Experiments were conducted to characterize the influence of texture and impact velocity on the dynamic, high-strain, tensile extrusion of zirconium. Bullet-shaped samples were machined from a clock-rolled, highly textured Zr plate. Specimens in two orthogonal directions were tested: the extrusion direction aligned with either the in-plane (IP) rolling or the through-thickness (TT) direction of the plate. The post-extrusion microstructure and texture evolution were examined using electron backscatter diffraction microscopy and modeled using the viscoplastic self-consistent model. It was found that extrusion deformation was accomplished through a combination of twinning and slip with their relative activity greatly depending on the initial texture. In this regard, higher elongations in the IP samples as compared to the TT samples were observed at similar test velocities. This difference in ductility is discussed in terms of the material’s ability to accommodate plastic deformation. Due to the availability of a larger number of slip systems with relatively high Schmid factors in the IP samples under this configuration, plastic deformation by prismatic slip can be easily achieved, resulting in larger elongations. On the contrary, for TT samples, twinning preceded deformation by slip. This sequential deformation process, driven by the need to reorient the microstructure favorably to slip, led to diminished elongations to failure.     

Determination of Thermoelectric Module Efficiency: A Survey

The development of thermoelectrics (TE) for energy conversion is in the transition phase from laboratory research to device development. There is an increasing demand to accurately determine the module efficiency, especially for the power generation mode. For many TE, the figure of merit, ZT, of the material sometimes cannot be fully realized at the device level. Reliable efficiency testing of thermoelectric modules is important to assess the device ZT and provide end-users with realistic values for how much power can be generated under specific conditions. We conducted a general survey of efficiency testing devices and their performance. The results indicated a lack of industry standards and test procedures. This study included a commercial test system and several laboratory systems. Most systems are based on the heat flow meter method, and some are based on the Harman method. They are usually reproducible in evaluating thermoelectric modules. However, different systems often showed large differences that are likely caused by uncertain heat loss and thermal resistance. Efficiency testing is an important capability for the thermoelectric community to improve. A follow-up international standardization effort is planned.     

Higher-Order Adaptive Finite Difference Methods for Fully Nonlinear Elliptic Equations

We introduce generalised finite difference methods for solving fully nonlinear elliptic partial differential equations. Methods are based on piecewise Cartesian meshes augmented by additional points along the boundary. This allows for adaptive meshes and complicated geometries, while still ensuring consistency, monotonicity, and convergence. We describe an algorithm for efficiently computing the non-traditional finite difference stencils. We also present a strategy for computing formally higher-order convergent methods. Computational examples demonstrate the efficiency, accuracy, and flexibility of the methods.     

Self Assembly–Assisted Additive Manufacturing: Direct Ink Write 3D Printing of Epoxy–Amine Thermosets

The use of self‐assembling, pre‐polymer materials in 3D printing is rare, due to difficulties of facilitating printing with low molecular weight species and preserving their reactivity and/or functions on the macroscale. Akin to 3D printing of small molecules, examples of extrusion‐based printing of pre‐polymer thermosets are uncommon, arising from their limited rheological tuneability and slow reactions kinetics. The direct ink write (DIW) 3D printing of a two‐part resin, Epon 828 and Jeffamine D230, using a self‐assembly approach is reported. Through the addition of self‐assembling, ureidopyrimidinone‐modified Jeffamine D230 and nanoclay filler, suitable viscoelastic properties are obtained, enabling 3D printing of the epoxy–amine pre‐polymer resin. A significant increase in viscosity is observed, with an infinite shear rate viscosity of approximately two orders of magnitude higher than control resins, in addition to, an increase in yield strength and thixotropic behavior. Printing of simple geometries is demonstrated with parts showing excellent interlayer adhesion, unachievable using control resins.