• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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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.

• 대한치과의사협회지
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• 제42권1호통권416호
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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.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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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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• 제47권1호
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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.

• 터널과지하공간
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• 제21권4호
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• pp.320-327
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• 2011

본 연구는 ○○ 석회석 광산의 화강암 폐석을 이용한 부순 모래를 전색재로 이용하기 위하여 그 현장의 주변에서 쉽게 구할 수 있는 바다 모래, 강 모래, 점토와 물의 전색재와 동일한 조건으로 모르타르 블록의 시험발파를 통해 전색효과에 대한 비교가 이루어졌다. 이때 모르타르 블록은 폭 50 cm, 길이 50 cm와 높이 70 cm로 제작하였다. 전색재료들에 대한 물리.역학적 특성을 알아보기 위하여 체가름 시험, 직접전단시험과 압출시험이 수행되었다. 모르타르 발파시험에서 전색길이 10 cm 및 20 cm에 대하여 폭발 충격압에 따른 강봉의 축방향 변형율과 전색재의 분출속도가 동적 변형율 측정기에 의해 측정되었다. 강봉의 축방향 변형율은 화강암 부순 모래가 가장 크게 나타났으며, 전색재의 분출속도는 물을 전색재로 사용하였을 때 가장 작은 값을 보이고 있다. 이 결과는 사용된 전색재의 발파 공내 다짐단위중량, 입도분포, 전단저항 및 압출시험결과와 상호 연관성을 보이고 있다. 전색재의 분출속도와 축방향 변형률은 서로 지수적으로 반비례하는 경향을 나타낸다.

• 동력기계공학회지
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• 제20권6호
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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.

• 대한안전경영과학회지
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• 제25권1호
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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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• 제56권1호
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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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• 제11권5호
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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.

• 대한소아치과학회지
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• 제36권4호
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• pp.613-618
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• 2009

구치부 매복은 1% 이내로 드문 편이지만 저위 교합, 반대 악궁 치아의 정출, 인접치 경사로 인한 공간 부족 등의 문제가 발생하게 된다. 구치부 치아는 교합 및 악골 발육에 관여하는 기능적으로 중요한 치아이므로 초기 혼합 치열기부터 지속적인 방사선 사진을 찍어 매복 여부를 관찰해야 한다. 매복의 원인에는 치근 발육의 저하, 과잉치, 낭종, 치아종, 유착 등이 있다. 첫 번째 증례에서는 초진 시 치근 발육이 1/2이하라서 자발적 맹출을 기대하였지만 2/3이상 발육 시에도 맹출 하지 못하여 외과적 노출 및 교정적 견인을 시함하였다. 두 번째 증례는 낭종을 포함하는 매복 구치를 주소로 내원하였고 낭종 크기가 작고 인접 부위에 주요한 해부학적 구조물이 없어 완전한 적출술을 시행 후 교정적 견인을 하였다. 교정적 견인 시 해당 치아에 직접 어태치먼트(attachment)를 붙인 후 악하고 지속적인 힘을 적용하는 것이 유착, 외흡수, 치주 부착 소실 등의 부작용이 나타나지 않는다. 또한 고정식 장치를 사용하면 환자의 협조도가 필요 없고 맹출 공간을 확보하면서 호선상에 매복치를 견인 할 수 있다. 본 증례에서는 매복 구치를 외과적 노출 및 교정적 견인을 통해 교합상으로 배열을 하여 양호한 결과를 얻었기에 보고하는 바이다.