706 research outputs found

    Finding efficient frontier of process parameters for plastic injection molding

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    Product quality for plastic injection molding process is highly related with the settings for its process parameters. Additionally, the product quality is not simply based on a single quality index, but multiple interrelated quality indices. To find the settings for the process parameters such that the multiple quality indices can be simultaneously optimized is becoming a research issue and is now known as finding the efficient frontier of the process parameters. This study considers three quality indices in the plastic injection molding: war page, shrinkage, and volumetric shrinkage at ejection. A digital camera thin cover is taken as an investigation example to show the method of finding the efficient frontier. Solidworks and Moldflow are utilized to create the part's geometry and to simulate the injection molding process, respectively. Nine process parameters are considered in this research: injection time, injection pressure, packing time, packing pressure, cooling time, cooling temperature, mold open time, melt temperature, and mold temperature. Taguchi's orthogonal array L27 is applied to run the experiments, and analysis of variance is then used to find the significant process factors with the significant level 0.05. In the example case, four process factors are found significant. The four significant factors are further used to generate 34 experiments by complete experimental design. Each of the experiments is run in Moldflow. The collected experimental data with three quality indices and four process factors are further used to generate three multiple regression equations for the three quality indices, respectively. Then, the three multiple regression equations are applied to generate 1,225 theoretical datasets. Finally, data envelopment analysis is adopted to find the efficient frontier of the 1,225 theoretical datasets. The found datasets on the efficient frontier are with the optimal quality. The process parameters of the efficient frontier are further validated by Moldflow. This study demonstrates that the developed procedure has proved a useful optimization procedure that can be applied in practice to the injection molding process

    Tailored Iterated Greedy metaheuristic for a scheduling problem in metal 3D printing

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    This article contributes to the additive manufacturing-based production planning literature by developing a Mixed-Integer Linear Programming (MILP) formulation for the Identical Parallel 3D-Printing Machines Scheduling Problem considering batching, multiple build platforms of restricted sizes, and sequence-independent setup times. Besides, a customized metaheuristic, named the Tailored Iterated Greedy (TIG) Algorithm is developed to solve the new optimization problem. TIGā€™s performance is evaluated through extensive numerical analysis and using a new testbed. It is shown that the customized computational mechanisms improve the optimization performance; statistical analysis is supportive of the significance of the resulting improvements. The developed mathematical model and optimization algorithm can be considered the basis for future developments in the optimization literature of additive manufacturing

    An investigation on helical gear pair stresses incorporating misalignment and detail modification

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    A finite element approach to investigating the dynamic behavior of helical gear pairs (HGPs) by incorporating misalignment error and detail modifications of tip relief and face-width crowning is presented. Basing on the C code and derived tooth profile formulas, fine finite element models of helical gear pair (HGP) can be constructed parametrically. Also, all elements on the driven teeth surfaces are numbered to identify individual dynamic stresses. After analysis settings, the dynamic contact and fillet bending stresses of a theoretic HGP are first calculated. Then, the maximum stresses with misalignment error are also obtained. Finally, the effect of tooth modification on the dynamic stresses of HGPs with the misalignment errors is discussed. The result shows modification with tip relief and face-width crowning can reduce the dynamic responses caused by the impact contact of HGPs

    The Complete Chloroplast Genome of Ginkgo biloba Reveals the Mechanism of Inverted Repeat Contraction

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    We determined the complete chloroplast genome (cpDNA) of Ginkgo biloba (common name: ginkgo), the only relict of ginkgophytes from the Triassic Period. The cpDNA molecule of ginkgo is quadripartite and circular, with a length of 156,945 bp, which is 6,458 bp shorter than that of Cycas taitungensis. In ginkgo cpDNA, rpl23 becomes pseudo, only one copy of ycf2 is retained, and there are at least five editing sites. We propose that the retained ycf2 is a duplicate of the ancestral ycf2, and the ancestral one has been lost from the inverted repeat A (IRA). This loss event should have occurred and led to the contraction of IRs after ginkgos diverged from other gymnosperms. A novel cluster of three transfer RNA (tRNA) genes, trnY-AUA, trnC-ACA, and trnSeC-UCA, was predicted to be located between trnC-GCA and rpoB of the large single-copy region. Our phylogenetic analysis strongly suggests that the three predicted tRNA genes are duplicates of trnC-GCA. Interestingly, in ginkgo cpDNA, the loss of one ycf2 copy does not significantly elevate the synonymous rate (Ks) of the retained copy, which disagrees with the view of Perry and Wolfe (2002) that one of the two-copy genes is subjected to elevated Ks when its counterpart has been lost. We hypothesize that the loss of one ycf2 is likely recent, and therefore, the acquired Ks of the retained copy is low. Our data reveal that ginkgo possesses several unique features that contribute to our understanding of the cpDNA evolution in seed plants

    Survival and breakthrough: A case study of evolutionary change in a state-owned enterprise

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    This study examines the processes undertaken by a state-owned enterprise to overcome limitations and successfully reverse its decline through moderate, gradual and small-scale evolutionary change. This paper utilizes the "social process research model" to analyze and record organizational changes at Jiangnan Resort, and further observes strategic countermeasures employed to address crises and successful management of organizational change. Results from our study suggest that organizational evolutionary change strategies should include institutionalization strategies, development of marketing channels, festival event marketing, placement marketing, product packaging strategies, niche market segmentation, service quality enhancement, and manpower flexibility strategies. Key factors in change management include Total Quality Management (TQM), Management by Objective (MBO), organizational members understanding of urgency and need of change, gaining support through education and communication, employee empowerment and participation, and institutionalizing change. The resulting information can serve as a reference for future qualitative research and development of strategic concepts for organizations planning to adopt evolutionary change into their companies

    Effects of natto extract on endothelial injury in a rat model

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    Vascular endothelial damage has been found to be associated with thrombus formation, which is considered to be a risk factor for cardiovascular disease. A diet of natto leads to a low prevalence of cardiovascular disease. The aim of the present study was to investigate the effects of natto extract on vascular endothelia damage with exposure to laser irradiation. Endothelial damage both in vitro and in vivo was induced by irradiation of rose bengal using a DPSS green laser. Cell viability was determined by MTS assay, and the intimal thickening was verified by a histological approach. The antioxidant content of natto extract was determined for the free radical scavenging activity. Endothelial cells were injured in the presence of rose bengal irradiated in a dose-dependent manner. Natto extract exhibits high levels of antioxidant activity compared with purified natto kinase. Apoptosis of laser-injured endothelial cells was significantly reduced in the presence of natto extract. Both the natto extract and natto kinase suppressed intimal thickening in rats with endothelial injury. The present findings suggest that natto extract suppresses vessel thickening as a synergic effect attributed to its antioxidant and anti-apoptosis properties

    Crosstalk between transcription factors and microRNAs in human protein interaction network

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    <p>Abstract</p> <p>Background</p> <p>Gene regulatory networks control the global gene expression and the dynamics of protein output in living cells. In multicellular organisms, transcription factors and microRNAs are the major families of gene regulators. Recent studies have suggested that these two kinds of regulators share similar regulatory logics and participate in cooperative activities in the gene regulatory network; however, their combinational regulatory effects and preferences on the protein interaction network remain unclear.</p> <p>Methods</p> <p>In this study, we constructed a global human gene regulatory network comprising both transcriptional and post-transcriptional regulatory relationships, and integrated the protein interactome into this network. We then screened the integrated network for four types of regulatory motifs: single-regulation, co-regulation, crosstalk, and independent, and investigated their topological properties in the protein interaction network.</p> <p>Results</p> <p>Among the four types of network motifs, the crosstalk was found to have the most enriched protein-protein interactions in their downstream regulatory targets. The topological properties of these motifs also revealed that they target crucial proteins in the protein interaction network and may serve important roles of biological functions.</p> <p>Conclusions</p> <p>Altogether, these results reveal the combinatorial regulatory patterns of transcription factors and microRNAs on the protein interactome, and provide further evidence to suggest the connection between gene regulatory network and protein interaction network.</p

    A lack of association between genetic polymorphisms in beta-defensins and susceptibility of psoriasis in Taiwanese: A caseā€“control study

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    AbstractBackgroundGenetic predisposition of the inflammatory-host response may affect the development of psoriasis. Previous studies have shown that copy number variations (CNVs) of Ī²-defensin genes (DEFB) are associated with the susceptibility of psoriasis in Caucasian populations.ObjectivesThis study aimed to assess the role of the CNVs of the DEFB4 gene and functional variants in the DEFB1 gene in Taiwanese patients with psoriasis.MethodsIn total, 196 patients with psoriasis and 196 control individuals were analyzed for the presence of the DEFB4 CNVs using the paralogue ratio test, and also for the DEFB1 polymorphisms rs11362, rs1800972, and rs1799946, using a polymerase chain reaction.ResultsNone of the polymorphisms were found to be associated with psoriasis. The distribution of DEFB4 genomic CNVs did not significantly differ between the control group and psoriasis group. The frequencies of patients who carried a greater than the median (ā‰„ 5) number of copies did not significantly differ in patients with psoriasis and controls. The multivariate analysis similarly revealed that the DEFB4 CNVs were not associated with psoriasis (odds ratioĀ =Ā 1.03, 95% confidence intervalĀ =Ā 0.89ā€“1.19, pĀ =Ā 0.720). No significant difference was detected in the genotype and allele distribution for any of the individual DEFB1 polymorphisms between the cases and the controls. Finally, the overall haplotype frequency profiles derived from the three polymorphisms did not significantly differ between the cases and the controls.ConclusionOur results do not suggest that these genetic variants of the Ī²-defensin genes contribute to the genetic background of psoriasis in Taiwanese patients
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