Cooling system has an important role in the injection molding process in terms of not only productivity and quality, but also mold-making cost. In this paper, a conformal cooling channel with an array of baffles is proposed for obtaining uniform cooling over the entire free-form surface of molded parts. A new algorithm for calculating temperature distribution through molding thickness, mold surface temperature and cooling time was presented. The relation among cooling channels' configuration, process parameters, mold material, molding thickness and temperature distribution in the mold for a given polymer is expressed by a system of approximate equations. This relation was established by the design of experiment and response surface methodology based on an adequate physical-mathematical model, finite difference method and numerical simulation. By applying this approximate mathematical relation, the optimization process for obtaining target mold temperature, uniform temperature distribution and minimizing the cooling time becomes more effective. Two case studies were carried out to test and validate the proposed method. The results show that present approach improves the cooling performance and facilitates the mold design process in comparison to the trial-and-error simulation-based method.
Besides the solid free-form fabrication technology, milling operation is an alternative applicable method to make complex cooling channels conform to the surface of the mold cavity. This paper presents the U-shape milled groove conformal cooling channels and proposes the design optimization process in order to obtain an optimal cooling channels' configuration and target mold temperature. The relation between the cycle averaged thermal behavior of the mold cavity and the two-dimensional configuration of cooling channels was first investigated thoroughly by an analytical method. Design of experiment and 2D simulation were done to obtain the mold wall temperature and to check the feasibility of the analytical method. The optimization process of the free-form conformal cooling channels is based on the combination of both analytical method and 3D CAE simulation. The analytical step relies on explicit mathematic formulas, so it can approach the neighboring optimal solution quickly. Subsequently, the three-dimensional heat transfer simulation is applied to fine-tune the optimization results. A case study for a plastic car fender was investigated to verify the feasibility of the proposed method. The results show that conformal cooling channel gives a uniform cooling, reducing the cooling time and increasing the molded part's quality with less effort of plastic designers and high computational efficiency.
The house fly, Musca domestica L. (Diptera: Muscidae), is involved in phoretic movement of pathogenic agents, but it has a very efficient defense mechanism against infection. It is believed that antimicrobial peptides play a significant role in the defense system of the house fly. Here, we isolated a peptide from the immunized house fly pupae, measured its molecular mass (3987.6 Da) by matrix-assisted laser desorption ionization/time of flight-mass spectrometry, and determined its amino acid sequence by using the Procise Protein Sequencing System (Applied Biosystems, Foster City, CA). The peptide was confirmed as a member of the insect defensin family. It displayed high activity against gram-positive bacteria but lower activity against gram-negative bacteria and fungi. Reverse transcription-polymerase chain reaction showed that the house fly defensin gene was constitutively expressed in naive pupae and strongly up-regulated after immunization. House fly defensin is an amphiphilic peptide with a structure similar to that of the CSalphabeta scaffold of insect defensin A from the flesh fly, Phormia terraenovae Robineau-Desvoidy. To our knowledge, this is the first isolated and characterized house fly antimicrobial peptide, and our work may provide useful information for developing pharmacologically active antimicrobial agents.
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