직업과 나

이상진 한국사법행정학회 1960 사법행정 Vol.1 No.3

Fabrication of Nano-Sized β-TCP Powder by an Organic-Inorganic Solution Route

이상진,고신일,Myung-Hyun Lee,Nam-Sik Oh 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.4

Highly sinterable, nano-sized β-tricalcium phosphate (TCP) powder was fabricated by an organic-inorganic solution route. Calcium nitrate and phosphoric acid were dissolved in D.I. water and 5 wt% polyvinyl alcohol (PVA) solution was added. The PVA was used as an organic carrier for the precursor gel. The dried precursor gel was fully crystallized to β-TCP at 1000 oC in an air atmosphere. As well, in the calcination process, the NOx and CO2 gases from the calcium nitrate and PVA polymer made the precursor gel to a soft and porous powder. The synthesized β-TCP powder was agglomerated showing nano-sized primary particles. The ball-milled and compacted β-TCP powder was fully densified at 1200 oC for 1 h. In particular, the sintered β-TCP showed pure β phase without phase transformation to α. In this process, the Ca/P ratio for stoichiometric β- TCP was adjusted by the control of phosphoric acid content. Highly sinterable, nano-sized β-tricalcium phosphate (TCP) powder was fabricated by an organic-inorganic solution route. Calcium nitrate and phosphoric acid were dissolved in D.I. water and 5 wt% polyvinyl alcohol (PVA) solution was added. The PVA was used as an organic carrier for the precursor gel. The dried precursor gel was fully crystallized to β-TCP at 1000 oC in an air atmosphere. As well, in the calcination process, the NOx and CO2 gases from the calcium nitrate and PVA polymer made the precursor gel to a soft and porous powder. The synthesized β-TCP powder was agglomerated showing nano-sized primary particles. The ball-milled and compacted β-TCP powder was fully densified at 1200 oC for 1 h. In particular, the sintered β-TCP showed pure β phase without phase transformation to α. In this process, the Ca/P ratio for stoichiometric β- TCP was adjusted by the control of phosphoric acid content.

Discussion on Social Aspects of Sustainability of Community: Focusing on the Naturally Formed Communities and the Boundary with New Development

이상진 대한건축학회지회연합회 2012 대한건축학회연합논문집 Vol.14 No.3

Sustainability has become one of the most important issues to dominate all other agenda in modern society. Most agenda regarding sustainability tends to focus on ecological or environmental sustainability. However, careful review of people's collective responses reveals that social aspects are more critical in determining sustainability of a city. Ecological sustainability, which mainly focusing on energy issues, can not be achieved in a city where social integrity is poor. For people to live in a city, social issues in a community may dominate all other issues since a community's allurement mainly comes from sociological attractions, such as good neighborhood. Thus, social integrity can be as much important as ecological issues to determine sustainability at least in a city. This paper aims to discuss the factors which affect social sustainability. Borrowing principles from nature to evaluate sustainability, two groups of factors are discussed for social aspects of sustainabilty; one group is connectivity/territoriality, the other is diversity/social contacts. Once precedent theories are reviewed to frame the discussion, two communities are selected to test the frame for analysis. Findings from the study reveal that two groups of factors, connectivity/territoriality and diversity/social contacts, are distinguishedly appeared from both communities.

Free Vibration Analysis of Elastic Bars using Isogeometric Approach

이상진,박경섭 대한건축학회 2011 Architectural research Vol.13 No.3

A study on the free vibration analysis of elastic bar is described in this paper. In order to determine the natural frequencies of bars, a bar element is developed by using isogeometric formulation. The B-spline is introduced to represent the geometry of bar and the same geometric definition is also used to define its unknown displacement field in isogeometric formulation. Therefore, the stiffness and mass matrices are derived by the order-free B-spline basis function. The efficiency and accuracy of the present isogeometric bar element is demonstrated by using several numerical tests. From numerical results, it is found to be that the present isogeometric element produces very accurate natural frequencies of bars. Finally, the present isogeometric solutions are provided as future reference solutions.

Isogeometric Analysis of Laminated Plates under Free Vibration

이상진 대한건축학회 2014 Architectural research Vol.16 No.3

A plate element is developed by using isogeometric approach in order to determine natural frequencies of laminated composite plates. Reissner-Mindlin (RM) assumptions is adopted to consider the shear deformation and rotatory inertia effect. All terms required in isogeometric element formulation are consistently derived by using Non-uniform rational B-spline surface (NURBS) definition. Gauss quadrature rule is used to form the element stiffness matrix and separately Lobatto quadrature rule is used to calculate element mass matrix. The capability of the present plate element is demonstrated by using numerical examples. From numerical tests, the present isogeometric element produces reliable numerical results for both thin and thick plate situations.

A Form-finding Technique for Three-dimensional Spatial Structures

이상진 대한건축학회 2013 Architectural research Vol.15 No.4

A form-finding technique is proposed for three-dimensional spatial structures. Two-step discrete finite element (FE) mesh generator based on computer aided geometric design (CAGD) is introduced and used to control the shape of three-dimensional spatial structures. Mathematical programming technique is adopted to search new forms (or shapes) of spatial structures. For this purpose, the strain energy is introduced as the objective function to be minimized and the initial volume (or the initial weight) is considered as constraint function. Numerical examples are carried out to test the capability of the proposed form-finding techniques and provided as benchmark tests.

Synthesis and characterization of strontium titanate powder via a simple polymer solution route

이상진,Pradheep Thiyagarajan,이만종 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.4

A simple chemical route has been used to synthesize highly sinterable strontium titanate (SrTiO3) powders using titanium isopropoxide, strontium nitrate and ethylene glycol. This method utilizes complexation-polymerization using ethylene glycol as an organic carrier, which leads to compositional homogeneity and fine particle sizes. The calcined SrTiO3 powder showing a porous nature was fully crystallized to a cubic phase at 1,300 oC for 1 hour. Through ball-milling the porous SrTiO3 powders with particle sizes of 200-300 nm were easily obtained, which was sintered to a bulk density of 4.8 g/cm3 at 1,400 oC for 1 h with a grain size of approximately 6.0 mm. The relative dielectric constant and loss tangent of SrTiO3 sintered at 1,400 oC for 1 hour were 2078 and 0.022, respectively.

Vibration and Buckling of Thick Plates using Isogeometric Approach

이상진,김하룡 대한건축학회 2013 Architectural research Vol.15 No.1

A study on the free vibration and linear buckling analyses of thick plates is described in this article. In order to determine the natural frequencies and buckling loads of plates, a plate element is developed by using isogeometric approach. The Non-uniform B-spline surface (NURBS) is used to represent both plate geometry and the unknown displacement field of plate. All terms required in isogeometric formulation are consistently derived by NURBS definition. The capability of the present plate element is demonstrated by using several numerical examples. From numerical results, it is found to be that the present isogeometric element can predict accurate natural frequencies and buckling loads of plates.

Characteristics of calcium phosphate powders synthesized from cuttlefish bone and phosphoric acid

이상진,이용천,윤영수 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.6

Fine calcium phosphate powders were fabricated by using recycled cuttlefish bone. A raw cuttlefish bone easily turned to CaO by a calcining process and the calcined cuttlefish bone was mixed with phosphoric acid by a wet, ball-milling method. The crystalline phases of the heated mixtures were dependent on the mixing ratio (wt%) of the calcined cuttlefish bone to phosphoric acid. In a wide mixing ratio range of 1:1.1-1:1.7 wt%, calcium phosphates were synthesized and fully crystallized HAp and β-TCP were observed at about 900°C and above. The synthesized powders showed fine particles of below 0.5 μm in size. In this study, the crystalline development and Ca/P molar ratios of the synthesized calcium phosphate powders were studied by X-ray diffractometry and chemical analysis using ICP AES. In addition, the microstructures of the cuttlefish bone and synthesized calcium phosphate powders were examined by scanning electron microscopy.

94 GHz 대역의 높은 격리 특성의MIMIC single balanced cascode 믹서

이상진,안단,이문교,문성운,방석호,백태종,권혁자,전병철,윤진섭,이진구 대한전자공학회 2007 電子工學會論文誌-SD (Semiconductor and devices) Vol.44 No.9

In this paper, the high isolation and wideband 94 GHz MIMIC(Millimeter-wave Monolithic Integrated Circuit) single balanced cascode mixer was designed and fabricated. Also, we designed and fabricated a 3 dB tandem coupler which has a high isolation and wideband characteristic. The single balanced resistive mixer which does not require an external IF balun was designed using the 0.1 μm InGaAs/InAlAs/GaAs metamorphic HEMT (High Electron Mobility Transistor). The DC characteristics of MHEMT's are 665 mA/mm of drain current density, 691 mS/mm of maximum transconductance. The current gain cut-off frequency(fT) is 189 GHz and the maximum oscillation frequency(fmax) is 334 GHz. A 94 GHz single balanced cascode mixer was fabricated using our 0.1 ㎛ MHEMT MIMIC process. From the measurements, the fabricated couplers showed wideband characteristics. The conversion loss of single balanced cascode mixer was 9.8 dB at an LO power of 10.9 dBm. The LO to RF isolation of single balanced cascode mixer was 29.5 dB at 94 GHz. We obtained in this study a higher LO-RF isolation compared to some other single balanced mixers. 본 논문에서는 높은 격리특성과 광대역 특성을 갖고 IF 발룬을 필요로 하지 않는 94 GHz MIMIC(Millimeter-wave Monolithic Integrated Circuit) single balanced cascode 믹서를 설계 및 제작하였다. 또한 믹서의 높은 격리특성과 광대역 특성을 위한 94 GHz 대역의 3 dB tandem 커플러를 설계 및 제작하였다. MIMIC single balanced cascode 믹서는 0.1 ㎛ InGaAs/InAlAs/GaAs Metamorphic HEMT (High Electron Mobility Transistor)를 이용하여 설계 및 제작되었다. 제작된 MHEMT는 드레인 전류 밀도 665 mA/mm, 최대 전달컨덕턴스(Gm)는 691 mS/mm를 얻었으며, RF 특성으로 fT는 189 GHz, fmax는 334 GHz의 양호한 성능을 나타내었다. 94 GHz MIMIC 믹서의 개발을 위해 MHEMT의 비선형 모델과 CPW 라이브러리를 구축하였으며, 이를 이용하여 MIMIC 믹서를 설계하였다. 설계된 믹서는 본 연구에서 개발된 MHEMT MIMIC 공정을 이용해 제작되었다. 94 GHz MIMIC single balanced cascode 믹서의 측정결과 변환손실 특성은 LO 신호의 크기가 10.9 dBm 일 때 94 GHz에서 9.8 dB의 양호한 특성을 나타내었다. 제작된 믹서의 LO-RF 격리도는 94 GHz에서 29.5 dB 그리고 100 GHz에서 39.5 dB의 측정 결과를 얻었다. 또한 제작된 믹서는 외부의 IF 발룬을 필요하지 않아 소형화가 가능??. 본 논문에서 설계 및 제작된 94 GHz MIMIC single balanced cascode믹서는 기존의 balanced 믹서와 비교하여 높은 격리 특성을 나타내었다.