• KSBB Journal
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• 제16권1호
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• pp.66-70
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• 2001

순수한 초임계 이산화탄소를 이용하여 camptothecin(CPT)와 10-hydroxy camptothecin(HCPT) 추출 시험을 결과, 이들은 각각 유기용매 메탄올 추출에 비교하여 3%와 2% 밖에 추출되지 않았다. 보조용매로 메탄올과 에탄올을 이용하여 CPT와 HCPT를 추출하면 추출 효율이 상승됨을 확인할 수 있었다. 특히 에탄올 보다 메탄올이 효율이 좋았다. 따라서 보조용매 적용에 관련된 여러 조건들을 최적화 하였다. 메탄올을 보조용매로 사용하는 경우에 보조용매의 농도가 증가할수록 추출 효율도 증가하였고 16% 이상에서는 추출 효율이 완만하게 증가하였다. 또한 추출은 온도에 따라 크게 영향을 받지 않아으나 온도에 따라 약간 증가하는 경향을 보였다. 초임계 추출에서 압력의 영향을 살펴본 결과 250 bar까지 압력이 증가할수록 추출 효율은 증가하였다. Acetate ion을 공급하여 추출 실험을 수행하였으나 CPT나 HCPT 모두 ion pairing agent의 영향은 없었다. 본 시스템과 같은 solid/fluid 추출 시스템에서 추출 효율에 영향을 크게 미치는 3가지 요소 (용해도, 확산, 및 matrix)중 확산의 영향을 살펴보았다. 여러 기하학적 모델 중 matrix가 구형인 hot-ball model로 확산게수를 계산하였다. 본 시스템에서 보조용매를 포함한 초임계 유체의 $D/r^2$ 값은 0.0072 $min^{-1}$로서 순수한 메탄올 유기용매 추출보다 큰 값을 보였다.

• 구강회복응용과학지
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• 제33권1호
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• pp.55-62
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• 2017

무치악 환자를 수복할 때 임플란트 피개의치를 이용한 치료법은 전통적인 총의치의 문제점인 저작시 동통, 의치의 부족한 유지와 안정을 포함하는 기능저하 문제 등을 해결할 수 있는 방법이다. $Locator^{(R)}$ (Zest Anchors LLC, Espandido, USA) 어태치먼트는 임플란트 피개의치에 사용되는 어태치먼트 중 수직적으로 필요한 공간이 가장 적고, 나일론 부품에 따라 유지력 조절이 용이하다. 하지만 Ball이나 Bar에 비해 기능시 부품의 마모로 유지력이 빠르게 감소하는 특징이 있어 가급적 임플란트 간 각도가 최소가 되도록 식립하려는 노력이 필요하다.

• 한국재료학회지
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• 제25권1호
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• pp.43-47
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• 2015

$Zn(BH_4)_2$ was prepared by milling $ZnCl_2$ and $NaBH_4$ in a planetary ball mill in an Ar atmosphere, and XRD analysis, SEM observation, FT-IR analysis, DTA, and TGA were performed for synthesized $Zn(BH_4)_2$ samples. 90 wt% $MgH_2$+1.67 wt% $Zn(BH_4)_2(+NaCl)$+5 wt% Ni+1.67 wt% Ti+1.67 wt% Fe (named $90MgH_2+1.67Zn(BH_4)_2(+NaCl)$+5Ni+1.67Ti+1.67Fe) samples were also prepared by milling in a planetary ball mill in an $H_2$ atmosphere. The gas absorption and release properties of the $Zn(BH_4)_2(+NaCl)$ and $90MgH_2+1.67Zn(BH_4)_2(+NaCl)_2(+NaCl)$+5Ni+1.67Ti+1.67Fe samples were investigated. An FT-IR analysis showed that $Zn(BH_4)_2$ formed in the $Zn(BH_4)_2(+NaCl)$ samples prepared by milling $ZnCl_2$ and $NaBH_4$. At the first cycle at $320^{\circ}C$, $90MgH_2+1.67Zn(BH_4)_2(+NaCl)$+5Ni+1.67Ti+1.67Fe absorbed 2.95 wt% H for 2.5 min and 4.93 wt% H for 60 min under 12 bar $H_2$, and released 1.46 wt% H for 10 min and 4.57 wt% H for 60 min under 1.0 bar $H_2$.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제45권4호
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• pp.199-206
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• 2019

Objectives: In mandibular edentulism, the treatment option with a two-interforaminal implant-retained bridge and a removable partial denture is rarely evaluated in literature. The aim of this in vitro study was to evaluate the stress distribution of this treatment option by comparing it with traditional treatment options with interforaminal implants in the edentulous mandible. Materials and Methods: Two interforaminal implants were placed in a formalin-fixed cadaver mandible, and overdentures with three different types of attachments were fabricated: (1) two ball attachments and an overdenture, (2) a Dolder bar and an overdenture, and (3) screw-retained two-implant inter-canine porcelain fused to a metal bridge and an implant-assisted removable denture (IARD) with precision attachments. Three biting conditions were generated for each denture type, and the strains were documented under vertical loading of 100 N. Results: The calculated strain values from measured strains in all measurement sites and loading conditions for the screw-retained two-implant intercanine porcelain fused to a metal bridge and a cast framework partial denture with precision attachments situation were lower than in the other scenarios (P<0.05). Conclusion: Within the limitations of the present study, it can be concluded that an IARD may be a reasonable and valuable alternative to ball attachments or a bar in two interforaminal implants, especially when the patients prefer to be able to show their teeth even when they take out their removable dentures.

• 한국수소및신에너지학회논문집
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• 제10권1호
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• pp.27-40
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• 1999

Mg 및 Ni chips을 사용하여 $Mg_2NiH_x$ 수소저장합금을 Planetary Ball Mill M/C로 제조하였으며, 합금화 과정 중에 미치는 분위기 수소압의 영향을 고찰하였다. XRD분석결과 1:30의 장입비에서는 24시간 합성조건일 경우 10 bar이상의 분위기에서 $Mg_2NiH_x$ 상이 발견되었으며 48시간 합성할 경우에는 5 bar 이상의 분위기에서 나타났다. 1:66의 장입 조건에서는 24, 48시간 모두 5 bar 이상의 분위기에서 $Mg_2NiH_x$ 가 검출되었다. 합금화 초기에 만들어지는 것으로 생각되는 $MgH_x$ 로 인하여 전 공정에 걸쳐 미반응 Ni가 잔류하였으며 TG 분석결과 합금화 과정 중에 흡수된 수소저장량은 수소압의 변화에 따라 1.1 ~ 3.9 wt%에 이르는 것으로 나타났다. SEM 관찰 결과 동일 공정 조건에서는 분위기 수소압의 증가가 합금화 결과 최종적으로 얻어지는 미세입자와 그 군집체의 형상 및 크기 변화에 큰 영향을 미치지 못하는 것으로 나타났다.

• 대한기계학회논문집A
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• 제31권10호
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• pp.993-998
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• 2007

To verify the 2D or 3D positioning accuracy of a multi-axes stage is not easy, particularly, in the case the moving path of the stage is not linear. This paper is a study on a measuring method for the curved path accurately. A machine vision technique is used to trace the moving path of two-axes stage. To improve the accuracy of machine vision, a zoom lens is used for the 2D micro moving path. The accuracy of this method depends of the CCD resolution and array align accuracy with the zoom lens system. Also, a further study for software algorithm is required to increase the tracing speed. This technique will be useful to trace a small object in the 2D micro path in real-time accurately.

• 충청수학회지
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• 제13권1호
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• pp.131-138
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• 2000

Let D be the open unit disk in the complex plane $\mathbb{C}$. For any q > 0, the operator $Q_q$ defined by $$Q_qf(z)=q\int_{D}\frac{f(\omega)}{(1-z{\bar{\omega}})^{1+q}}d{\omega},\;z{\in}D$$. maps $L^{\infty}(D)$ boundedly onto $B_q$ for each q > 0. In this paper, weighted Bloch spaces $\mathcal{B}_q$ (q > 0) are considered on the open unit ball in $\mathbb{C}^n$. In particular, we will investigate the possibility of extension of this operator to the Weighted Bloch spaces $\mathcal{B}_q$ in $\mathbb{C}^n$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.305-311
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• 1993

In recent years, it has been variously developed for testing the accuracy of circular motion of NC machine tools, for example Telescoping Ball Bar Method by Bryan,Circular Test Method by Knapp and r $_{- \theta}$ Mathod by Tsutsumi etc., but it is not yet settled in the code of measuring methods of motion errors of NC machine tools, because of errors of measuring units and sensors, and also especially the difficulties of centering of measuring units. In this paper, in use of magnetic type linear scale with resolution of 0.5 .mu. m and tick pulses come out from computer, it has become possible for detecting of linear displacement of radial errors and measuring of revolution angle of circular motion of NC machine tools.

• 한국산업융합학회 논문집
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• 제23권2_2호
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• pp.313-321
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• 2020

In this paper, two types of linear actuation methods for the previously proposed adaptive gripper are presented, which includes actual parallelogram inside a five-bar mechanism and has the advantages of smaller actuation torque and larger stroke over the commercial adaptive gripper by RobotiQ. The forward/inverse kinematics and statics analyses for two types of linear actuations are derived. From the inverse kinematics and statics analyses, linear actuation type I is selected and the gripper prototype is designed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1705-1708
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• 2003

The purpose of this study is to investigate the manufacturing technique on the U type Draw-Bending of inner grooved tube. This bending process make the U shape tube by Hair Pin Bending machine. The U type tube requires the quality of product that satisfy sufficient conditions for a heat exchanger. The mandrel components act the important roles that prevent wrinkles and keep the shape of cross section of bended tube at bending process. We performed the FEM simulation using LS-DYNA software and the bending test of inner groove tube and then, compared bending simulation with bending test results about mandrel ball diameter, mandrel position and optimal clearance between mandrel and tube.