• Ocean Systems Engineering
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• 제11권1호
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• pp.43-58
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• 2021

In the present work, a 3D numerical model is proposed to study local scouring around single vertical piers with different cross-section shapes under steady-current flow. The model solves the flow field and sediment transport processes using a coupled approach. The flow field is obtained by solving the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations in combination with the k-ω SST turbulence closure model and the sediment transport is considered using both bedload and suspended load models. The proposed model is validated against the empirical measurements of local scour around single vertical piers with circular, square, and diamond cross-section shapes obtained from the literature. The measurement of scour depth in equilibrium condition for the simulations reveal the differences of 4.6%, 6.7% and 13.1% from the experimental measurements for the circular, square, and diamond pier cases, respectively. The model displayed a remarkable performance in the prediction of scour around circular and square piers where horseshoe vortices (HSVs) have a leading impact on scour progression. On the other hand, the maximum deviation was found in the case of the diamond pier where HSVs are weak and have minimum impact on the formation of local scour. Overall, the results confirm that the prediction capability of the present model is almost independent of the strength of the formed HSVs and pier cross-section shapes.

• 대한기계학회논문집
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• 제17권6호
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• pp.1456-1464
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• 1993

본 논문에서는 다이아몬드 공구를 사용한 절삭과정에 대하여 절삭력 관계식을 제안하고, 이를 실제 천연 다이아몬드 공구를 이용하여 알루미늄 합금을 절삭하는 실험해석을 통하여 절삭력을 예측하는 모델을 세우고자 한다.

• 수산해양기술연구
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• 제30권3호
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• pp.172-181
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• 1994

The mesh selectivity of diamond and suare mesh cod-ends at the Southern Korean Sea and the East China Sea were compared for Pampus argenteus, Trachurus japonicus, Trichiurus lepturus. Selection trials were carried out using diamond and square mesh cod-end by trouser type cod-end with cover net. of which the mesh cod-end has four types : A(51.2mm), B(70.2mm), C(77.6mm), D(88.0mm). Selection curves and selection parameters were calculated using a logistic model. The results obained are summarized as follows : 1. Harvest fish : In B. C and D type selection range and fifty percent selection length of the square mesh were about 21mm, 11mm : 12mm, 18mm and 34mm, 5mm higher than those of the diamond mesh, respectively. Selection factor of master curve for the diamond mesh was 1.54 and for the square mesh was 1.68. The optimum mesh size for the diamond mesh was 97.4mm and for the square mesh was 89.3mm, the difference was 8.1mm. 2. Horse mackerel : In A type, selection range was nearly the same for the diamond and the square mesh, but fifty percent selection length of the square mesh was 43mm higher than the diamond mesh. In B. C and D type, selection range and fifty percent selection length of the square mesh were about 6mm, 3mm : 24mm, 21mm and 11mm, 42mm higher than those of the diamond mesh, respectively. Selection factor of master curve for the diamond mesh was 2.37, for the square mesh was 2.77. The optimum mesh size for the diamond mesh was 78.1mm and for the square mesh was 66.8mm, the difference was 11.3mm. 3. Hair tail : In A, B and C type, selection range of the square mesh was about 34mm, 8mm, 60mm higher than those of the diamond mesh. Fifty percent selection length for the diamond mesh was about 5mm, 7mm, 8mm higher than that of the square mesh. Selection factor of master curve for the diamond mesh was 3.11, for the square mesh was 3.48. The optimum mesh size for the diamond mesh was 64.3mm and for the square mesh was 57.5mm, the difference was 6.8mm.

• 한국정밀공학회지
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• 제21권11호
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• pp.38-45
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• 2004

This paper discusses the minimum cutting thickness with a continuous chip in sub-micrometer order precision diamond cutting. An ultra precision cutting model is proposed, in which the tool edge radius and the friction coefficient are the principal factors determining the minimum cutting thickness. The experimental results verify the proposed model and provide various supporting evidence. In order to reduce the minimum cutting thickness a vibration cutting method is applied, and the effects are investigated through a series of experiments under the same conditions as conventional cutting method.

• 정보관리학회지
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• 제39권3호
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• pp.195-216
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• 2022

본 연구는 대학도서관에서 제공하는 서비스 가치를 극대화하기 위하여 서비스디자인 방법론을 대학도서관에 적용하였다. 이를 위하여 서비스디자인 모형인 '더블다이아몬드모델'(Double Diamond Model)을 대학도서관에 적용, 서비스디자인 도구인 퍼소나(Persona), 고객여정지도(Customer Journey Map), 터치포인트(Touch Points)를 활용하였다. 서비스디자인을 대학도서관에 반영하기 위하여 주제와 관련된 문헌 및 선행연구를 고찰하였으며, 설문조사 및 이용자와 사서면담, 현장조사를 통해 상황별 이슈를 발견하고 퍼소나와 상황시나리오를 도출하였다. 나아가 설정된 퍼소나의 상황별 행동과 이용자의 감정변화에 대한 정보를 종합하여 이를 고객여정지도로 시각화하고 3개 분야 11개 항목의 서비스 개선안을 제안하였다. 본 연구는 특정 서비스를 개선하기보다 서비스 개선방안을 도출하기까지의 과정에 주안점을 두었다. 또한, 대학도서관 서비스개선 및 새로운 서비스 방안을 제시하는 것이 본 연구의 목적이었다. 이를 통해 실질적인 서비스 개선 방안을 대학도서관에 적용하였다는 것에 본 연구의 의의가 있다.

• 응용통계연구
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• 제19권2호
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• pp.361-368
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• 2006

이차원 범주형 자료를 시각적으로 표현하는 이차원과 삼차원 그래프는 많이 존재한다. 그중에서 Li등(2003)은 삼차원 그래프를 이차원 평면에 투영시키는 다이아몬드 그래프를 제안하였다. 여기서 세번째 차원은 면적과 높이 그리고 길이가 관찰값에 대응하는 다이아몬드 모양으로 대체하였다. 본 논문에 서는 이차원 자료에 대하여는 두 범주형 변수의 독립성을 검정하기 위하여 다이아몬드 그래프를 이용한다. 그리고 삼차원 이상의 자료에 대해서는 자료에 가장 적합한 로그선형모형을 설정하는데 활용할 수 있다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.71-74
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• 1995

Diamond shaping is one of the machining strategies to make the optical micro-groove molds,and it is especially useful when rhe component is an assembly of the linear micro-groove array. A mirror-like surface and arbitrary crose-sectional curve can be easily made by diamond. Howerver, the cutting speed of shaping is relatively lower than that of the other cutting methods, and there exist an unstable cutting conditions that generate the chatter. This study is focused on the modeling of the simplified self-induced chatter of the diamond shapping. Form the chatter model and experiments, it is found that the unstable cutting conditions exist wwhen the depth of cut is low and cutting speed is high.

• 통상정보연구
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• 제13권3호
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• pp.249-274
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• 2011

농식품 수출활성화는 국내농업의 소득창출을 위한 새로운 전환기를 제공하는 방안이라는 인식이 확산되고 있다. 최근 한류열풍으로 국내 농식품에 대한 인식이 확산됨에 따라 농식품 수출은 새로운 도전이면서 기회이기도 하다. 그러나 국내 농업이 가지고 있는 구조적 문제와 수출시장 진입에 관한 중장기적 전략부재로 인해 수출시장 경쟁력이 향상되지 못하고 있는 설정이다. 이러한 환경 하에서 본 연구는 우리나라 수출농업 활성화를 위해 농식품 수출부문의 경쟁력을 제고시킬 수 있는 포괄적인 접근의 필요성을 인식하고 농식품 수출분야에 경쟁력의 개념을 도입하여 농식품의 수출정쟁력 결정요인에 대하여 분석하였다. 농식품 수출부문의 국가 경쟁력 비교분석을 위해서는 종합적인 시각에서 농식품 수출부문을 분석 할 수 있는 평가모델과 측정척도를 적용하는 것이 중요하다. 따라서 비농업분야에서 경쟁력 결정요인을 찾기 위해 다양하게 적용된 포터의 경쟁력 모델을 중심으로 농식품 수출부문의 경쟁력을 비교분석하였다. 이를 바탕으로 우리나라의 농식품 수출부문의 국가경쟁력 강화방안을 모색하고자 한다.

• 한국정밀공학회지
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• 제13권10호
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• pp.154-160
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• 1996

The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surfice. However, as the accuracy requirement gets tighter and desired surface cnotours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function to result in the estimated dapth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in additn to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using the precision dynamoneter. Based on the parameter estimation of cutting dynamics and the admitance model-based nanodynamic control scheme, simulation results are shown.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1352-1355
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• 1996

The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surface. However, as the accuracy requirement gets tighter and desired surface contours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function to result in the estimated depth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in addition to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using the precision dynamometer. Based on the parameter estimation of cutting dynamics and the admittance model-based nanodynamic control scheme, simulation results are shown.