Optimization of injection molding design. Part I: Gate location optimization

The placement of a gate in an injection mold is one of the most important variables of the total mold design. The quality of the molded part is greatly affected by the gate location, because it influences the manner in which the plastic flows into the mold cavity. Some defects, such as weldline and overpack, can be effectively controlled only by the gate location. Therefore, the product quality can be greatly improved by determining the optimum gate location. In this paper, we develop a general methodology for gate location optimization. We first quantify quality in terms of flow simulation outputs. We can thus assess detrimental effects such as warpage and dimensional instability as a function of the independent variable, which is in this case the gate location. Next we develop methods to search for the optimum gate location. The search method introduced in this paper is a method that combines a deterministic hill climbing search with a stochastic annealing search method. The method is appropriately called simulated annealing and hill climbing (SANHIL). The criteria used for evaluation during the search process are a function of the flow simulation outputs. We demonstrate the success of the method for a complex industrial mold. The approach is applicable to any complex mold geometry and any plastic.     

Road to Next Generation Mobile Networks: An Evolutionary Dynamics Approach

One of the major challenges that mobile operators (MOs) are faced with nowadays is the transition to 4th Generation (4G) mobile communication technologies. The main reason for this lies on the reluctance of MOs to invest in a new technology without being sure about its success. The current paper investigates the decision-making procedures of a MO that wishes to migrate from its current technology type to 4G. Traditionally, the decision of deploying a new technology has been based on the analysis of similar implementations in other countries. However, such approaches can be inefficient and time consuming, as there are discrepancies concerning the technological progress among different countries. To this end, the authors employ evolutionary game theory to model the interactions of the MO’s decisions and the subscribers’ needs, and propose a practical and efficient qualitative model that identifies the circumstances under which the transition towards 4G networking can be facilitated. Specifically, the mathematical foundation of the decision making process is provided and the key role of the charging price and the quality of experience by the subscribers for using 4G connectivity is proven. With the process of 4G deployment still ongoing, this paper aims to present an analysis that can be used supplementary to the decision process of a MO that aims to evolve his network.     

Gelation and phase separation in maltodextrin-caseinate systems

A range of rheological techniques, including small deformation isothermal runs following quenching, controlled rate heating profiles, mechanical spectra, and large deformation strain sweeps and creep compliance testing, were employed in the investigation of maltodextrin—sodium caseinate aqueous dispersions. The concentration dependence, viscoelastic ratio and melting profiles of shear moduli for concentrated maltodextrin samples suggest a highly aggregated, enthalpically linked biopolymer gel. By contrast, the caScinate particles form a ‘pasty’ solid at low temperatures with a high viscous component, which upon moderate heating reverts readily into an entropically driven liquid body. Mixing of the polymers results in a composite system whose phase inversion from a maltodextrin continuous network with discontinuous protein inclusions to a caScinate dispersion suspending the polysaccharide particles is determined by the weight ratio of the two components in the blend. The overall strength of the composite has been related to the mechanical functions of the individual components, and the idea of kinetically trapped mixed gels has been put forward to rationalize the solvent partition between the two constituent phases. Results were used to advance the conclusions reached from work on other mixed biopolymer systems carried out in this laboratory.     

A New Family of Ultralow Loss Reversible Phase‐Change Materials for Photonic Integrated Circuits: Sb2S3 and Sb2Se3

Phase‐change materials (PCMs) are seeing tremendous interest for their use in reconfigurable photonic devices; however, the most common PCMs exhibit a large absorption loss in one or both states. Here, Sb₂S₃ and Sb₂Se₃ are demonstrated as a class of low loss, reversible alternatives to the standard commercially available chalcogenide PCMs. A contrast of refractive index of Δn = 0.60 for Sb₂S₃ and Δn = 0.77 for Sb₂Se₃ is reported, while maintaining very low losses (k < 10^?5) in the telecommunications C‐band at 1550 nm. With a stronger absorption in the visible spectrum, Sb₂Se₃ allows for reversible optical switching using conventional visible wavelength lasers. Here, a stable switching endurance of better than 4000 cycles is demonstrated. To deal with the essentially zero intrinsic absorption losses, a new figure of merit (FOM) is introduced taking into account the measured waveguide losses when integrating these materials onto a standard silicon photonics platform. The FOM of 29 rad phase shift per dB of loss for Sb₂Se₃ outperforms Ge₂Sb₂Te₅ by two orders of magnitude and paves the way for on‐chip programmable phase control. These truly low‐loss switchable materials open up new directions in programmable integrated photonic circuits, switchable metasurfaces, and nanophotonic devices.     

Benzodithiophene Hole‐Transporting Materials for Efficient Tin‐Based Perovskite Solar Cells

Developing efficient interfacial hole transporting materials (HTMs) is crucial for achieving high‐performance Pb‐free Sn‐based halide perovskite solar cells (PSCs). Here, a new series of benzodithiophene (BDT)‐based organic small molecules containing tetra‐ and di‐triphenyl amine donors prepared via a straightforward and scalable synthetic route is reported. The thermal, optical, and electrochemical properties of two BDT‐based molecules are shown to be structurally and energetically suitable to serve as HTMs for Sn‐based PSCs. It is reported here that ethylenediammonium/formamidinium tin iodide solar cells using BDT‐based HTMs deliver a champion power conversion efficiency up to 7.59%, outperforming analogous reference solar cells using traditional and expensive HTMs. Thus, these BDT‐based molecules are promising candidates as HTMs for the fabrication of high‐performance Sn‐based PSCs.     

Alicyclobacillus acidoterrestris in fruit juices and its control by nisin

Summary The acid-tolerant and heat-resistant bacterium Alicyclobacillus acidoterrestris is a spoilage problem in pasteurized and heat-treated fruit juices. In this study it was shown to grow in orange juice, grapefruit juice and apple juice to produce detectable taint at levels of about 10⁴–10⁵ c.f.u. ml⁻¹. Decimal reduction times were determined at 80 °, 90 ° and 95 °C in each juice and confirmed the heat-resistant nature of the spores under normal juice pasteurization conditions. They also confirmed that heat sensitivity increased with decreasing pH but that this effect was less pronounced at higher temperatures. The organism was, however, sensitive to the bacteriocin food preservative nisin. The presence of nisin during heating decreased the D value by up to 40% and the MIC for nisin against spores at 25 °C was only 5 International Units (IU) ml⁻¹. The results indicate that use of nisin is a potentially useful way of controlling this organism in fruit juices and fruit juice-containing products.     

In-depth analysis and evaluation of diffusive glioma models

Glioma is one of the most aggressive types of brain tumor. Several mathematical models have been developed during the past two decades, toward simulating the mechanisms that govern the development of glioma. The most common models use the diffusion-reaction equation (DRE) for simulating the spatiotemporal variation of tumor cell concentration. Nevertheless, despite the applications presented, there has been little work on studying the details of the mathematical solution and implementation of the 3-D diffusion model and presenting a qualitative analysis of the algorithmic results. This paper presents a complete mathematical framework on the solution of the DRE using different numerical schemes. This framework takes into account all characteristics of the latest models, such as brain tissue heterogeneity, anisotropic tumor cell migration, chemotherapy, and resection modeling. The different numerical schemes presented have been evaluated based upon the degree to which the DRE exact solution is approximated. Experiments have been conducted both on real datasets and a test case for which there is a known algebraic expression of the solution. Thus, it is possible to calculate the accuracy of the different models.     

Performance evaluation of a C-RAN supporting a mixture of random and quasi-random traffic

Wireless Networks - In this paper we consider a cloud radio access network (C-RAN) where the remote radio heads (RRHs) are separated from the baseband signal processing servers, named baseband...     

Engset multi‐rate state‐dependent loss models with QoS guarantee

We consider a single link loss system of quasi‐random input, described by the Engset multirate loss model (EnMLM). Blocked calls may once reattempt to be connected to the system requiring less bandwidth; then the system is described by the single retry model for finite sources (f‐SRM). The EnMLM and the f‐SRM are extended with the single threshold finite source model (f‐STM), where calls may attempt to be connected to the system with less bandwidth requirements, according to the link occupancy, before blocking occurs. We focus on CBP equalization in the EnMLM, f‐SRM and f‐STM, under the bandwidth reservation (BR) policy. For this analysis, we apply two approximate methods, the Roberts' method and the method of reverse transition rates (RTR), which lead to a recursive CBP calculation. We evaluate the accuracy of the above models under the BR policy by comparing the analytical with simulation CBP results, based on the relative approximation errors (RAE). The results are highly satisfactory because they show that the proposed models (formulas) lead to small RAE. Copyright © 2005 John Wiley & Sons, Ltd.