• 한국분말재료학회지
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• 제13권6호
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• pp.421-426
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• 2006

The microstructural and mechanical properties of Al-Si alloyed powder, prepared by gas atomization fallowed by hot extrusion, were studied by optical and scanning electron microscopies, hardness and wear testing. The gas atomized Al-Si alloy powder exhibited uniformly dispersed Si particles with particle size ranging from 5 to $8{\mu}m$. The hot extruded Al-Si alloy shows the average Si particle size of less than $1{\mu}m$. After heat-treatment, the average particle size was increased from 2 to $5{\mu}m$. Also, mechanical properties of extruded Al-Si alloy powder were analyzed before and after heat-treatment. As expected from the microstructural analysis, the heat-treated samples resulted in a decrease in the hardness and wear resistance due to Si particle growth. The friction coefficient of heat-treated Al-Si alloyed powder showed higher value tough all sliding speed. This behavior would be due to abrasive wear mechanism. As sliding speed increases, friction coefficient and depth and width of wear track increase. No significant changes occurred in the wear track shape with increased sliding speed.

• 소성∙가공
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• 제31권3호
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• pp.160-166
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• 2022

The purpose of this study is to investigate the effects of combined addition of Ca and Y on the precipitation and age-hardening behavior of an extruded AZ91 alloy by conducting the aging treatment at 200 ℃ for hot-extruded AZ91 and AZ91-0.3Ca-0.2Y alloys. In the AZ91 alloy, many Mg₁₇Al₁₂ discontinuous precipitate (DP) bands formed during air cooling immediately after extrusion are present, whereas in the AZ91-0.3Ca-0.2Y alloy, a few DP bands and numerous Al₂Y, Al₈Mn₄Y, and Al₂Ca phase particles are distributed along the extrusion direction. The peak-aging time of the AZ91-0.3Ca-0.2Y alloy is 16 hours, twice that of the AZ91 alloy. Although both alloys have similar hardness before aging treatment, the hardness after peak-aging treatment (i.e., peak hardness) of the AZ91-0.3Ca-0.2Y alloy is higher than that of the AZ91 alloy, as 93.1 and 88.7 Hv, respectively. The microstructures of both peak-aged alloys comprise DPs and continuous precipitates (CPs). However, the peak-aged AZ91-0.3Ca-0.2Y alloy has a smaller amount of DPs and a larger amount of CPs than the peak-aged AZ91 alloy. Additionally, the inter-particle spacings of DPs and CPs in the former are significantly narrower than those in the latter. These results demonstrate that the addition of small amounts of Ca and Y to a commercial AZ91 alloy considerably affects the formation rate, size, and amount of CPs and DPs during aging and resultant age-hardening behavior.

• 대한방사선기술학회지:방사선기술과학
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• 제22권1호
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• pp.27-33
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• 1999

The classification of herniated intervertebral lumbar disc type is clinically important, as treatment method may be slightly different according to the type of herniated intervertebral disc. When 450 patients who suffered from herniated intervertebral lumbar disc were tested with Magnetic Resonance Imaging (MRI) to find out the type of herniated disc, the following findings were given : 1. The age of the patients investigated ranged from 15 to 83, and their mean age was 40. 2. The male patients were twice as many as the female patients, since the ratio of males to females was 300 : 150. 3. 118 patients suffered from a single herniated disc, and 332 patients were attacked with multi-herniated disc. 4. The types of single herniated disc were a protrusion for 50 patients (40%) and an extrusion for 40 patients (34%). The part of being herniated was an intervertebral disc between $L_4-L_5$ for 95 patients(80%) and the same disc between $L_5-S_1$ for 22 patients(19%). 5. The types of multi : -herniated disc were an protrusion for 67 patients(20%) and an extrusion for 70 patients(21%). Besides, 90 patients (28%) were the case that protrusion and extrusion coexisted simultaneously. The parts of being herniated were $L_3-L_4,\;L_4-L_5$ and $L_5-S_1$ for 53 patients(16%), $L_3-L_4$ and $L_4-L_5$ for 57 patients(17%), and $L_4-L_5$ and $L_5-S_1$ for 139 patients(42%).

• 한국약용작물학회지
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• 제26권5호
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• pp.417-429
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• 2018

Background: The objective of this study was to make colloidal dispersions of the active compounds of radix of Angelica gigas Nakai that could be charaterized as nano-composites using hot melt extrusion (HME). Food grade hydrophilic polymer matrices were used to disperse these compound in aqueous media. Methods and Results: Extrudate solid formulations (ESFs) mediated by various HPMCs (hydroxypropyl methylcelluloses) and Na-Alg polymers made from ultrafine powder of the radix of Angelica gigas Nakai were developed through a physical crosslink method (HME) using an ionization agent (treatment with acetic acid) and different food grade polymers [HPMCs, such as HP55, CN40H, AN6 and sodium alignate (Na-Alg)]. X-ray powder diffraction (XRD) analysis confirmed the amorphization of crystal compounds in the HP55-mediated extrudate solid formulation (HP55-ESF). Differential scanning calorimetry (DSC) analysis indicated a lower enthalpy (${\Delta}H=10.62J/g$) of glass transition temperature (Tg) in the HP55-ESF than in the other formulations. Infrared fourier transform spectroscopy (FT-IR) revealed that new functional groups were produced in the HP55-ESF. The content of phenolic compounds, flavonoid (including decursin and decursinol angelate) content, and antioxidant activity increased by 5, 10, and 2 times in the HP55-ESF, respectively. The production of water soluble (61.5%) nano-sized (323 nm) particles was achieved in the HP55-ESF. Conclusions: Nano-composites were developed herein utilizing melt-extruded solid dispersion technology, including food grade polymer enhanced nano dispersion (< 500 nm) of active compounds from the radix of Angelica gigas Nakai with enhanced solubility and bioavailability. These nano-composites of the radix of Angelica gigas Nakai can be developed and marketed as products with high therapeutic performance.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2018년도 춘계학술발표회
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• pp.72-72
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• 2018

The root of Angelica gigas Nakai (AGN) is used as a traditional herbal medicine in Korea for the treatment of many diseases. However, a major challenge associated with the usage of the active compounds from AGN is their poor water solubility. Therefore, this work aimed to enhance the solubility of active compounds by a chemical (viz. surfactant) and physical (hot melt extrusion) crosslinking method (CPC). Infrared Fourier transform spectroscopy (FT-IR) revealed multiple peaks in extrudate solids representing new functional groups including carboxylic acid, alkynes and benzene derivatives. Differential scanning calorimetry (DSC) analysis of the extrudate showed lower glass transition temperature (Tg) and lower enthalpy (${\Delta}H$) (Tg: $43^{\circ}C$; ${\Delta}H$: <6 (J/g)) compared to the non-extrudate (Tg $68.5^{\circ}C$; ${\Delta}H$: 123.2) formulations. X-ray powder diffraction (XRD) analysis revealed amorphization of crystal materials in extrudate solid. In addition, nanonization, enhanced solubility and higher extraction of phenolic compounds were achieved in the extrudate solid. Among the different extrudates, acetic acid- and Span 80-mediated formulations showed superior extractions. We conclude that the CPC method successfully enhanced the production of amorphous nano dispersions from extrudate solid formulations.

• 한국약용작물학회지
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• 제26권4호
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• pp.317-327
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• 2018

Background: The root of Angelica gigas Nakai is used as a traditional herbal medicine in Korea for the treatment of many diseases. However, the poor water solubility of the active components in A. gigas Nakai is a major obstacle to its bioavailability. Methods and Results: This work aimed at enhancing the solubility of the active compounds of A. gigas Nakai by a chemical (using a surfactant) and physical (hot melt extrusion, HME) crosslinking method. Fourier transform infrared spectroscopy revealed multiple peaks in the case of the extrudate solids, attributable to new functional groups including carboxylic acid, alkynes, and benzene derivatives. Differential scanning calorimetry analysis showed that the extrudate soilid had a lower glass transition temperature ($T_g$) and enthalpy (${\Delta}H$) ($T_g:43^{\circ}C$, ${\Delta}H$ : < 6 J/g) as compared to the non-extrudate ($T_g:68.5^{\circ}C$, ${\Delta}H:123.2$) formulations. X-ray powder diffraction analysis revealed the amorphization of crystalline materials in the extrudate solid. In addition, enhanced solubility (53%), nanonization (403 nm), and a higher amount of extracted phenolic compounds were achieved in the extrudate solid than in the non-extrudate (solubility : 36%, nanonization : 1,499 nm) formulation. Among the different extrudates, acetic acid and span 80 mediated formulations showed superior extractions efficiency. Conclusions: HME successfully enhanced the production of amorphous nano dispersions of phenolic compound including decursin from extrudate solid formulations.

• 한방재활의학과학회지
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• 제26권1호
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• pp.87-93
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• 2016

Objectives To analyze the resorption of herniated lumbar intervertebral disc on MRI in patients who were treated with Korean Medicine. Methods 78 patients with lumbar disc herniation were included, 47 males and 32 females. Patients' diagnosis was based on magnetic resonance imaging (MRI). All of the patients were only treated with Korean Medicine for 6 months treatment, and underwent MRI examination twice, pre-treatment and post-treatment. MR images were assessed by reduction in diameter of T2-weighted image between pre-treatment and post-treatment, and analyzed by differences in sex, age and disc type. Results 91.2% (71 people) of total patients had extrusion type. Korean medicine treatment reduced lumbar disc herniation diameter of all the patients from 7.11 mm to 3.67 mm on average (p<0.001). The reduction of diameter in the male group was 3.52 mm on average. The reduction of diameter in the female group was 3.32 mm on average. The reduction of diameter was 3.28 mm in the group below age 29, 3.88 mm in the 30~39 age group, 3.39 mm in the 40~49 age group, and 2.71 mm in the above 50 age group on average. Conclusions The MRI results suggest that lumbar herniated disc can resorb with Korean Medicine treatment. The likelihood of lumbar disc resorption was higher at extrusion type. but there was not a significant difference between the sexes and between ages.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 춘계학술대회 논문집
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• pp.54-61
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• 1997

Furthermore the rothor pole, with a solid type, manufactured by cold forging process at present should dmploy 3 press lines which consist of total 7 processes. Since A.S.B. treatment is prerequisite for the press line, the 3 times of A.S.B. treatment requires a long lead time, with little contribution to the reduction in cost. The author has investigated, through this researach, the possibility of a new forging method for a rotor pole production with (1) 2 pass instead of 3 press lines (2) only one A.S.B. treatment instead of 3 ones (3) solid type instead of sectional type, and (4) improvment of material property during process using a modified forging process and a specially designed die.

• 대한치과교정학회지
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• 제29권1호
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• pp.129-136
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• 1999

유착, 부적절한 교정치료, 과잉치, 낭종, 비정상적인 맹출경로등의 국소적인 원인으로 인하여 구치부의 매복이 발생할 수가 있다. 매복치는 적절한 치료를 하지 않으면, 교합기능의 상실, 영구치의 상실, 대합치의 정출, 인접치의 치근흡수등을 야기 할 수가 있다. 매복치를 성공적으로 맹출유도하기 위해서는 매복치의 치근형성여부가 중요한 요소가 되며, 매복치의 치근형태, 주위환경등을 유의한 적절한 교정력이 가해져야 한다.

• 열처리공학회지
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• 제17권3호
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• pp.165-172
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• 2004

Compared with the hydroforming technology for steel, the hydroforming technology for aluminum has not been actively investigated. Recently, the hydroforming of high strength aluminum tubes has attracted great interest because of its good strength to weight ratio. In this study, front side member (FSM) is fabricated with the hydroforming of aluminum tube and the mechanical properties and dimensional accuracy of the hydroformed FSM is investigated. For hydroforming process, extruded aluminum tubes with ribs to improve the structural rigidity are used. To ensure the mechanical properties, the aluminum tubes are T6 heat-treated before hydroforming.