• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5352-5356
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• 2013

Plastic product manufacturing industry has usually focused on a mechanical and physical characteristics of molding. Recently, not only these characteristics but also the aesthetic value is significantly considering. Especially, the molding's gloss, which we can easily distinguish, is an important aesthetic point. In this study, it were investigated that the gloss variation of ABS moldings by changing injection conditions such as injection pressures, injection speed, holding pressures melt and mold temperatures by injection molding experiment. The experimental results revealed that the holding pressure was the most active condition on gloss of ABS molding.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.125-131
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• 2002

Surface defects in injection molded parts are due to the unsteady flow of polymer melt which are related to the geometries of cavity and gate, the operational conditions of injection and the rheological properties of polymer. In this study we have examined jetting phenomena in injection molding process for three kinds of PCs which have different molecular weight and structure, PBT and PC/ABS alloy with several injection speeds. We have used various cavity shapes that are tensile, flexural and impact test specimens with various gate and cavity thicknesses. Through this study we have observed that the formation of surface defect associated with jetting during filling stage in injection molding is strongly related to die swell. This means that the jetting is strongly affected by the elastic property rather than the viscous property in viscoelastic characteristics of molten polymer. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mold design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting and associated surface defects regardless of magnitude of elastic property. It also enlarges process window that can produce steady flow of polymer melt in injection molding.

• The Journal of the Korea Contents Association
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• v.17 no.7
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• pp.215-221
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• 2017

The purpose of present study was to assess whether Gd-EOB-DTPA with gadolinium-based contrast agent administration affects fat quantification using the two-point Dixon technique. Between April 2016 and September, 60 patients who underwent hepatic fat quantification using the two-point Dixon technique were divided into two group (normal liver donors=30, abnormal hepatic steatosis=30) and we compared the variability of mean fat fraction before and after administration Gd-EOB-DTPA. As a results, in both group, fat fraction after injection Gd-EOB-DTPA was significantly decreased (normal liver donors -33.8%, hepatic steatosis -47.2%) compared to before injection Gd-EOB-DTPA, suggesting that Gd-EOB-DTPA affects fat quatification using two-point Dixon technique. In conclusion, hepatic fat quantification using the two-point Dixon technique could maintain diagnostic value by acquiring images before administration Gd-EOB-DTPA.

• The KSFM Journal of Fluid Machinery
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• v.19 no.5
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• pp.50-60
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• 2016

A design methodology of the modeled test facility to conserve an injection performance of a passive safety injection system is proposed. This safety injection system is composed of a core makeup tank and a safety injection tank. Individual tanks are connected with pressure balance line on the top side and injection line on the bottom side. It is important to conserve the scaled initial injection flow rate and total injection time since this system can be operated by small gravity head without any active pumps. Differential pressure distribution of the injection line induced by the gravity head is determined by the vertical length and elevation of each tank. However, the total injection time is adjustable by the flow resistance coefficient of the injection line. The scaling methodology for the tank and flow resistance coefficient is suggested. A key point of this test facility design is a scaling analysis for the flow resistance coefficient. The scaling analysis proposed on this paper is based on the volume scaling law with the same vertical length to the prototype and can be extended to a model with a reduced vertical length. A set of passive injection test were performed for the tanks with the same volume and the different length. The test results on the initial flow rate and total injection time showed the almost same injection characteristics and they were in good agreement with the design values.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2003.03a
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• pp.122-127
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• 2003

• Journal of the Korea Construction Safety Engineering Association
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• s.36
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• pp.88-93
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• 2006

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.8 no.2
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• pp.204-209
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• 1997

In the treatment of spasmodic dysphonia, laryngeal injection of botulinum toxin has been reported to be successful. The treatment of adductor type spasmodic dysphonia with botulinum toxin type A injection using EMG was conducted in 24 patients and it's effect was compared with results from flexible nasopharyngoscopy guided injection(29 patients) and telelaryngoscopy guided injection(31 patients). Sixty two point five percent(62.5%) of patients using EMG and 75.8% of patients using flexible nasopharyngoscope and 90.0% of patients using telelaryngoscope reported that the patient's symptom was improved. The functional status of the patient's disorder was classified into low grades. The mean pre-injection grade for patients using EMG, flexible nasopharyngoscope and telelaryngoscope was 1.7, 1.6 and 2.1 respectively. And it was lowered to 1.0, 0.7 and 1.1 respectively after the injection. Results were similar(p＜0.05). As a self assessment method, patients were asked to rate their voice on a scale of 100. In this study, the mean pre-injection score was 66.3, 44.0 and 40.0 respectively. And it was improved to 74.8, 77.7 and 69.8 respectively after the injection. Among 23 patients who undergone above 3method, 17 patients(73.9%) told that EMG-guided botulinum injection was preferable method in its convenience and effectiveness. In conclusion, EMG guided botulinum toxin injection is an another effective method for the treatment of adductor type spasmodic dysphonia similar to telelaryngoscopy-guided injection and flexible nasopharyngoscopy guided injection.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.100-107
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• 2005

The present work covers a new ray tracing scheme of an injection-molded plastic lens linked with finite element analysis fur injection molding processes. The traditional ray tracing schemes have been based on the assumption that optical property of the lens is homogeneous throughout the entire volume. However, this assumption is quite unrealistic for injection-molded plastic lenses since material properties vary at every point due to injection molding effects. In order to consider non-homogeneous property of a lens, a modified ray tracing method is proposed in connection with finite element analysis of injection molding. Through the analysis of the injection molding process, the distribution of refractive indices can be obtained. This information is then utilized in the proposed ray tracing scheme based on finite element meshes so as to take into account variation of the refractive indices. The effect of mold temperature is also investigated through finite element analysis, and the relevant optical quality is evaluated through the proposed ray tracing simulation.

• Transactions of Materials Processing
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• v.12 no.1
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• pp.3-10
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• 2003

The formation of surface defects associated with Jotting in injection molding is related to the geometries of cavity and fate, operational conditions and the rheological properties of polymer. In this study we have examined jetting phenomena in injection molding process for the throe kinds of PCs which have different molecular weights and structures, PBT and PC/ABS alloy with several injection speeds. We have used various cavity shapes those are tensile, flexural and impact test specimens with various gates and cavity thicknesses. Through this study we have observed that the jetting is related to the dic swell of material. This means that the jotting is strongly affected by the elastic flow property rather than the viscous flow property in viscoelastic characteristics of molten polymer. Different resins have different elastic properties, and elastic flow behavior depends on the shear rate of flow, i.e. injection speed. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mole design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting regardless of amount of elasticity of polymer melt.

• Korea-Australia Rheology Journal
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• v.16 no.1
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• pp.27-33
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• 2004

Application of gas assisted injection molding has been expanded during last two decades because of many advantages such as design flexibility, dimensional stability, reduction of machine tonnages, and so on. However, the surface defects including hesitation mark and gloss difference are observed for thick parts. Difficulties in lay-out of the gas channel and processing condition are another disadvantages. Liquid gas assisted injection molding(LGAIM), in which a liquid with a boiling point lower than the temperature of the polymer melt is injected into the melt stream, and travels with the melt into the mold where it vaporizes and pushes the melt downstream and against the cavity walls to create hollow channels within the part, is a good alternative of the conventional gas assisted injection molding especially in manufacturing simple and very thick parts. Though this is a new frontier of the innovation in the injection molding industry, there is no guideline for the design and processing conditions. In this paper, theoretical analysis has been made to describe the hollow formation dynamics in LGAIM. This model provides an insight into LGAIM process: explains why LGAIM has advantages over conventional gas assisted injection molding, and gives a guideline for the design and processing conditions.