1,721,036 research outputs found
Prediction of shrinkage and warpage in consideration of residual stress in integrated simulation of injection molding
No full textThe accurate prediction of shrinkage and warpage of injection molded parts is important to achieve successful mold design with high precision. III this study, the numerical analysis of shrinkage and warpage of injection molded parts made of amorphous polymers was carried out in consideration of the residual stresses produced during the packing and cooling stages of injection molding. The temperature and pressure fields were obtained from the coupled analysis of the filling and post-filling stages. For residual stress analysis, a thermo-rheologically simple viscoelastic material model was introduced to consider the stress relaxation effect and to describe the mechanical behavior according to the temperature change. The effect of the additional material supply during the packing stage was modeled by assigning the reference strain. The deformation of injection molded parts after ejection induced by the residual stress and temperature change was analyzed using a linear elastic three-dimensional finite element approach. In order to verify the numerical predictions obtained from the developed program, the simulation results were compared with the available experimental data in the literature. In the case of residual stress, it was found that the present simulation results overpredicted the tensile residual stresses at the surface of injection molded parts. However, the predicted shrinkage was found to be: reasonable to describe the effects of processing conditions well. Finally, an analysis of the shrinkage and warpage was successfully extended for a part with a more complex curved shape. (C) 2000 Published by Elsevier Science Ltd.The authors are grateful for the grant from Korea Science and Engineering Foundation through the Engineering Reseach Center for Net Shape and Die Manufacturing at Pusan National University under which this work was possible
Structure of pyrrole on Ge(100)
No full textThe adsorption structures of pyrrole on a Ge(100) surface at low coverage have been investigated using ab initio density-functional theory (DFT) calculations. The most stable configuration is that the adsorbed pyrrole molecule with H dissociated forms a bridge between two down-Ge atoms of neighboring dimer rows through N-Ge bonding and C-Ge interaction. The corresponding simulated images explain well the flower-like features with a dark side observed in the experiment. Also, C-H dissociative structures are found to contribute as a minority to the features. A similar configuration to the most stable one, but with a dissociated H out of the region of interest, can explain the flower-like feature without a dark side. Finally, a C- and N-end-on configuration may be a possible candidate for bright protrusions in the STM images.KOSEF through the Center for Nanotubes and Nanostructured Composites and the Brain Korea 21 Project
Vertical digital thermooptic switch in polymer
No full textThe authors have proposed and fabricated a vertical digital thermooptic waveguide switch with polymer. It consists of two vertically stacked waveguides, a vertically sloped waveguide to connect them, and a heating electrode. Its vertical switching operation is based upon the mode evolution effect in a vertical branch waveguide. The transfer characteristics of the device exhibit the digital response. The measured crosstalk is lower than - 13 dB and the power consumption in the heating electrode is about 800 mW. The switching time is about 7 Ins. This device will be useful to increase the integration density of planar lightwave circuits
Adsorption and thermal stability of ethylene on Ge(100)
No full textWe have investigated the adsorption structures and thermal desorption behavior of C2H4 on Ge(100) using scanning tunneling microscopy (STM) and temperature programmed desorption (TPD) under ultrahigh vacuum (UHV). Ethylene molecules adsorb in two distinct bonding geometries: (i) on top of a single Ge-Ge dimer (on-top) and (ii) in a paired end-bridge between two neighboring Ge dimers within the same dimer row (paired end-bridge). Real-time STM images taken during the exposure of C2H4 to Ge(100) show that the on-top configuration dominates over the paired end-bridge configuration. The TPD measurements show that chemisorbed C2H4 desorbs from Ge(100) nondissociatively with two different desorption features, denoted as alpha (385 K) and beta (405 K). Desorption follows first-order kinetics for both states; the desorption energies of the alpha (385 K) and beta (405 K) states are 1.05 and 1.15 eV, respectively. These desorption energies are about 0.6 eV lower than those of ethylene on Si(100), indicating that the Ge-C bond is weaker than the Si-C bond. STM measurements carried out after annealing Ge surface at various temperatures indicate that the alpha and beta states correspond to the on-top and paired end-bridge configurations, respectively.KOSEF and the Center for Nanotubes
and Nanostructured Composites, the Brain Korea 21 Project, the Advanced Backbone IT Technology Development Project of the Ministry of Information and Communication, the National R&D Project for Nano Science and Technology
MicroRNA in exosomes isolated directly from the liver circulation in patients with metastatic uveal melanoma.
No full textBackground: Uveal melanoma is a tumour arising from melanocytes of the eye, and 30 per cent of these patients develop liver metastases. Exosomes are small RNA containing nano-vesicles released by most cells, including malignant melanoma cells. This clinical translational study included patients undergoing isolated hepatic perfusion (IHP) for metastatic uveal melanoma, from whom exosomes were isolated directly from liver perfusates. The objective was to determine whether exosomes are present in the liver circulation, and to ascertain whether these may originate from melanoma cells. Methods: Exosomes were isolated from the liver perfusate of twelve patients with liver metastases from uveal melanoma undergoing IHP. Exosomes were visualised by electron microscopy, and characterised by flow cytometry, Western blot and real-time PCR. Furthermore, the concentration of peripheral blood exosomes were measured and compared to healthy controls. Results: The liver perfusate contained Melan-A positive and RNA containing exosomes, with similar miRNA profiles among patients, but dissimilar miRNA compared to exosomes isolated from tumor cell cultures. Patients with metastatic uveal melanoma had a higher concentration of exosomes in their peripheral venous blood compared to healthy controls. Conclusions: Melanoma exosomes are released into the liver circulation in metastatic uveal melanoma, and is associated with higher concentrations of exosomes in the systemic circulation. The exosomes isolated directly from liver circulation contain miRNA clusters that are different from exosomes from other cellular sources.open112226sciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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