• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.98-101
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• 1999

The plastic instable flow phenomenon happens in practical forming process I. e. upsetting backward extrusion piercing indentation. And also it is difficult to control precisely the shape and dimensions of forming process. It is found that instabilities of the process are mainly connected with imperfection in the lubrication billet eccentricity inclined punch alignment. In view of the direct relationship between instable material flow and quality defects of the products and it is for better control of forming operation we should necessarily find out their phenomena. In this study we used the friction disturbance due to inclined punch angle and introduced the method considering kinematic hardening effect Analysis of upset forging is carried out using the rigid plastic FEM and slab method with eccentricity.

• The Journal of the Korean dental association
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• v.42 no.1 s.416
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• pp.7-14
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• 2004

Molar extrusion is a quite common problem in prosthodontic patients. It is caused due to the loss or infraocclusion of opposing teeth. A more conservative approach than reduction of the coronal part of extruded tooth is to intrude the malaligned molar orthodontically. Several authors have presented the cases of molar intrusion, by cither removable or fixed appliances. However, the design of those appliances was complex so that many teeth were included as an anchorage unit. This increased the patient's discomfort inevitably. Moreover, the results could be unpredictable. Instead of these conventional methods, skeletal anchorage has been suggested for ideal force system to intrude a molar without any side effects. Many recent clinical reports presented the cases using microscrew or miniplate as a direct anchorage, which included some limitation. The purpose of this report is to introduce the indirect skeletal anchorage for intrusion of extruded maxillary molar.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.855-856
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• 2006

In the present work, hot workability of particulate-reinforced Al6061-20%SiC composite produced by direct hot extrusion technique was studied. Uniaxial hot compression test at various temperatures and strain rates was used and the workability behavior was evaluated from the flow curves and the attendant microstructures. It was shown that the presence of SiC particles in the soft Al6061 matrix deteriorates the hot workability. Bulging of the specimens and flow lines were observed, which indicate the plastic instability during hot working. Microstructure of the composites after hot deformation was found to be heterogeneous, i.e. the reinforcement clusters were observed at the flow lines. The mechanism of deformation was found to be controlled primarily by dynamic recrystallization.

• Restorative Dentistry and Endodontics
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• v.47 no.1
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• pp.11.1-11.11
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• 2022

This study aimed to describe the outcomes of the GentleWave system (GW) (Sonendo) on root canal treatment. Published articles were collected from scientific databases (MEDLINE/PubMed platform, Web of Science, Scopus, Science Direct and Embase). A total of 24 studies were collected from August/2014 to July/2021, 20 in vitro and 4 clinical. GW System was not associated with extrusion of the irrigant, promoted faster organic dissolution than conventional syringe irrigation (CSI), passive ultrasonic irrigation (PUI) continuous ultrasonic irrigation (CUI) and EndoVac, reduced more bacterial DNA and biofilm than PUI and CUI, promoted higher penetration of sodium hypochlorite into dentinal tubules than PUI and CUI in vitro, and removed more intracanal medication than CSI and PUI. GW was able to remove pulp tissue and calcifications. Moreover, its ability to remove hard-tissue debris and smear layer was better than that of CSI, and its ability to remove root canal obturation residues was lower or similar to that of PUI, and similar to that of CSI and EndoVac. Regarding root canal obturation of minimally instrumented molar canals, GW was associated with high-quality obturation. Clinically, the success rate of endodontic treatment using GW was 97.3%, and the short-term postoperative pain in the GW group was not different from CSI. Further research, mainly clinical, is needed to establish whether GW has any advantages over other available irrigation methods.

• Tunnel and Underground Space
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• v.21 no.4
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• pp.320-327
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• 2011

In this study, for stemming effect in blast of the mortar block body, the crushed granite sand as fine aggregate, which is waste rock obtained at the ○○ limestone mine, was investigated to compare with stemming materials such as sea sand, river sand, clayed soil and water can be acquired easily at the field. The mortar block body was manufactured with the dimensions of 50 cm width, 50 cm length and 70 cm height. The direct shear and sieve separator test were performed, and the properties of friction resistance were analyzed by the extrusion test for five stemming materials. Axial strain of steel bar and ejection velocity of stemming materials due to the explosive shock pressure in blasthole with the stemming length of 10 cm and 20 cm in the mortar blast test were measured by the dynamic data acquisition system. Among stemming materials, axial strain showed the largest value at the crushed granite sand as fine aggregate, and the ejection velocity was the smallest value at the stemming of water. The results has shown correlate with harden unit weight in blasthole, particle size distribution, shear resistance, and extrusion strength of stemming materials. The ejection velocity of stemming material at the mouth of blasthole and the axial strain of steel bar in the inside of blasthole tend to be inversely proportional to each other, represent exponentially.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.40-45
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• 2016

The manufacturing process of large scaled Al 7050 alloy is difficult for the occurrence of solidification crack during casting. The aims of this study are the evaluations of microstructure and mechanical properties of extruded Al 7050 billet and ring forged one with large scale. Large scaled Al 7050 billet was casted by direct-chill casting process. The extruded and ring forged specimens were prepared from the casted ingot after residual stress relief and homogenization heat treatment, respectively. Microstructures, hardness and tensile test of the surface, middle and center part of each specimen were performed at room temperature. Sheared and elongated type grains were observed at the edge parts of surface and center area and its aspect ratios of grains were low and similar as 0.21 while that of middle area was closed to 0.92 value in ring forged Al 7050 alloy. The mechanical properties of extruded Al 7050 alloy were superior than those of ring forged one. The hardness values of surface and center part were slightly higher than that of middle part in ring forged Al 7050 alloy.

• Journal of the Korea Safety Management & Science
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• v.25 no.1
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• pp.7-14
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• 2023

We attempted to provide an overview of the laws and current state of the 3D printing industry in South Korea and around the world, using the annual industry surveys and the Wohler report. Additionally, we reviewed articles relating to the potential exposure to hazards associated with 3D printing using metal materials. In South Korea, there were 406 3D printing-related businesses, employing 2,365 workers, and the market size was estimated at 455.9 billion won in 2021. Globally, the average growth rate of the 3D printing industry market over the past 10 years was 27.4%, and the market size was estimated at $11.8 billion in 2019. The United States had the highest cumulative installation ratio of industrial 3D printers, followed by China, Japan, Germany, and South Korea. A total of 6,168 patents related to 3D printing were registered in the US between 2010 and 2019. Harmful factors during metal 3D printing was mainly evaluated in the powder bed fusion and direct energy deposition printing types, and there is a case of material extrusion type with metal additive filaments. The number, mass, size distribution, and chemical composition of particles were mainly evaluated. Particle concentration increases during the opening of the chamber or post-processing. However, operating the 3D printer in a ventilated chamber can reduce particle concentration to the background level. In order to have a safe and healthy environment for 3D printing, it is necessary to accumulate and apply knowledge through various studies.

• Clinical Endoscopy
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• v.56 no.1
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• pp.65-74
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• 2023

Background/Aims: Gastric varices (GV) are present in 25% of cirrhotic patients with high rates of rebleeding and mortality. Data on endoscopic ultrasound (EUS)-guided treatment in severe liver disease (model for end stage liver disease sodium [MELD-Na] >18 and Child-Turcotte-Pugh [CTP] C with GV) are scarce. Thus, we performed a retrospective comparison of endoscopic glue injection with EUS-guided therapy in cirrhotic patients with large GV. Methods: A retrospective study was performed in the tertiary hospitals of India. A total of 80 patients were recruited. The inclusion criteria were gastroesophageal varices type 2, isolated gastric varices type 1, bleeding within 6 weeks, size of GV >10 mm, and a MELD-Na >18. Treatment outcomes and complications of endoscopic glue injection and EUS-guided GV therapy were compared. Results: In this study, the patients' age, sex, liver disease severity (CTP, MELD-Na) and clinical parameters were comparable. The median number of procedures, injected glue volume, complications, and GV obturation were better in the EUS group, respectively. On subgroup analysis of the EUS method (e.g., direct gastric fundus vs. paragastric collateral [PGC] coil placement), PGC coil placement showed decreased coil requirement, less injected glue volume, decreased luminal coil extrusion, and increased successful GV obturation. Conclusions: EUS-guided treatment is more efficient and safer, and requires a smaller number of treatment sessions, as compared to endoscopic treatment in severe liver disease patients with large GV. Furthermore, PGC coil placement increases the complete obliteration of GV.

• Asian-Australasian Journal of Animal Sciences
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• v.11 no.5
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• pp.597-607
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• 1998

Processing is generally employed to alter the physical and chemical properties of feeds used in pig diets, using hammer/roller mills, pellet mills and extruders/expanders. The reported optimum particle sizes of corn are approximately $500{\mu}m$, $500-700{\mu}m$, $400-600{\mu}m$, for nursery, growing-finishing, and breeder pigs respectively. Optimum particle size of grains are affected by diet complexity. There was a trend towards reducing particle size in order to increase ADG in pigs fed a simple diet, though such was not the case for pigs fed a complex diet. Uniformity of particle size also affects the nutritional values of swine feeds. Uniform particle sizes would consistently give greater nutrient digestibilities. In terms of pellet quality, it is reported that a higher incidence of fmes in pelleted feeds has a direct correlation with poorer feed conversion ratio in pigs. Particle and pellet sizes are also very important for pelleting in terms of grinding, digestibility, stomach ulceration and pellet durability. A particle size of $600{\mu}m$, or slightly less, seemed optimal for com in fmishing pigs, and the 5/32 in. diameter pellets supported the best efficiencies of gain during nursery and finishing phases. Extruder and/or expander processes would allow the feed industry an increased flexibility to utilize a wider spectrum of feed ingredients, and improve pellet quality of finished feeds. It would appear that extruded or expanded diets containing highly digestible ingredients have little effect on the growth performance of pigs, and the feeding values of the feeds over pelleted diets were not improved as pigs grew. The extruder or expander is much more effective than a pelletizer in salmonella control. Gastric ulcerations and/or keratinizations were consistently reported in pigs fed mash and processed diets containing finely ground grains, whereas carcass quality was not affected by diet processing methods such as pelleting, extruding or expanding. In corn- or sorghum-based diets, the electrical energy consumption is 4-5 times higher in the expanding than in the pelleting process. But the expander's processing cost was half of that shown by an extruder. Finally, the decision of which feed processing technology to adopt would depend on the processing cost, and any potential improvement in growth performance and digestibilities of nutrients should offset the increased operating and capital costs related to the extruder/expander technology over mash or pelleting processes in pigs.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.4
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• pp.613-618
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• 2009

Impacted molars are not usual with the prevalence rate of less than 1%, however problems such as infraocclusion, extrusion of the opposite tooth and lack of space are caused. If molars are impacted, radiographic check-up and observations are needed as they play an important role in skeletal development and mastication. Causes of impaction are underdevelopment of roots, supernumerary teeth, cysts, odontomas, ankylosis and etc. In our first case, we present impacted molar which was surgically exposed and orthodontically traded. As the developmental state of the root was less than half at first visit, we observed until the root was 2/3 in its length and traction was carried out. The second case is orthodontic traded molar with compleate enucleation of the existing cysts. When trading impacted molars, direct bonding of attachments to the tooth and light continuous forces are recommended so as to ankylosis, external absorption and periodontal attachment loss avoid. Fixed appliances tract the teeth on arch and obtain eruption spaces without patient's cooperation. We report surgically exposed and orthodontically traded molars which resulted in good occlusion and patients satisfaction.