• 한국환경복원기술학회지
• /
• 제16권3호
• /
• pp.107-117
• /
• 2013

Problems in regard of ecological stability of urban ecosystem ensue from climate change and urbanization. Particularly, urban ecological conditions are deteriorating both quantitatively and qualitatively to a great extent. The present study aims to assess the current condition of selected sites (i. e. urban green zones and parks) in terms of preset assessment components; to find out problems and relevant solutions to improve the quality and quantity of parks and green zones; and ultimately to suggest some measures applicable to coping with climate change as well as to securing the ecological attributes of urban green zones and parks. According to the findings of this study, from quantitative perspectives, ecological attributes and responsiveness to climate change are high on account of the large natural-soil area(80%). By contrast, from qualitative perspectives including the planting structure (1 layer: 47%), the percentage of bush area(17%), the connectivity with surrounding green zones (independent types: 44%), the wind paths considered (5.6%), the tree species with high carbon absorption rates (20%), water cycles (17%), energy (8%) and carbon storage capacities(61%), ecological attributes and responsiveness to climate change were found very low. These findings suggest that the ecological values of urban parks and green zones should be improved in the future by conserving their original forms, securing natural-soil grounds and employing multi-layered planting structures and water bodies, and that responsiveness to climate change should be enhanced by planting tree species with high carbon storage capacities and obtaining detention ponds. In sum, robust efforts should be exerted in the initial planning stages, and sustained, to apply the methodology of green-zone development along with securing ecological attributes and responsiveness to climate change.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
• /
• pp.133-133
• /
• 1998

In the thin film alloy formation of the transition metals ion-beam-mixing technique forms a metastable structure which cannot be found in the arc-melted metal alloys. Sppecifically it is well known that the studies about the electronic structure of ion-beam-mixed alloys pprovide the useful information in understanding the metastable structures in the metal alloy. We studied the electronic change in the ion-beam-mixed ppt-Ct alloys by XppS and XANES. These analysis tools pprovide us information about the charge transfer in the valence band of intermetallic bonding. The multi-layered films were depposited on the SiO2 substrate by the sequential electron beam evapporation at a ppressure of less than 5$\times$10-7 Torr. These compprise of 4 ppairs of ppt and Cu layers where thicknesses of each layer were varied in order to change the alloy compposition. Ion-beam-mixing pprocess was carried out with 80 keV Ae+ ions with a dose of $1.5\times$ 1016 Ar+/cm2 at room tempperature. The core and valence level energy shift in these system were investigated by x-ray pphotoelectron sppectroscoppy(XppS) pphotoelectrons were excited by monochromatized Al K ａ(1486.6 eV) The ppass energy of the hemisppherical analyzer was 23.5 eV. Core-level binding energies were calibrated with the Fermi level edge. ppt L3-edge and Cu K-edge XANES sppectra were measured with the flourescence mode detector at the 3C1 beam line of the ppLS (ppohang light source). By using the change of White line(WL) area of the each metal sites and the core level shift we can obtain the information about the electrons pparticippating in the intermetallic bonding of the ion-beam-mixed alloys.

• 한국분말재료학회지
• /
• 제13권2호
• /
• pp.144-149
• /
• 2006

In this research we tried to make nano-sized TiNx by using planetary milling, and we made the composites double layered of titanium and nano-sized TiNx by using spark plasma sintering apparatus after mixing with the different ratio of pure titanium powder, and they were heat treated at $850^{\circ}C$ for 30 minutes. The crystal structures of nano-sized TiNx powders and the composites were analyzed by X-ray diffraction (XRD). The microstructures of the powders were analyzed by using scanning electron microscopy (FESEM) and the 40-50 nm size of nano-sized TiNx particle on the surface of agglomerated particles was investigated. With increasing the ratio of nano-sized TiNx of the composites, the microvickers hardness of the composites was increased.

• 한국해안·해양공학회논문집
• /
• 제24권4호
• /
• pp.247-256
• /
• 2012

본 연구는 다층지반으로 구성된 방조제의 침투변화에 따른 안정성을 검토하기 위하여 현장조사와 역해석 방법으로 투수계수와 침투수량을 결정하고, 제체의 변형량과 유실량 측정을 위하여 침투모형시험을 수행하여 가장 합리적인 수치해석 방법을 결정하였다. 검토결과 방조제는 다층지반구조물로 투수계수 차이에 의해 바닥보호공과 성토체 경계부에서 유실이 발생하고 이로 인해 방조제의 변형이 발생한다는 것을 예측할 수 있었다. 한편 침투모형 시험에 대한 수치해석결과 한계유속에 의한 방법은 실측치가 해석값보다 작게 나왔으나 그 경향이 유사하여 실제 단면에 적용 가능할 것으로 판단되었다.

• Applied Microscopy
• /
• 제22권2호
• /
• pp.66-74
• /
• 1992

In an attempt to produce transgenic amphibia, bacteriophage ${\lambda}-DNA$ was microinjected into fertilized eggs of Xenopus laevis, and the effect on early embryogenesis and the ultrastructural behavior of exogenous DNA were investigated. The effect of microinjected gene on embryonic development showed differences according to the concentration of injected DNA and the incubation temperature. Various concentrations of ${\lambda}-DNA$ were tested. Among those, microinjection of 1-2 ng DNA dissolved in 20 nl TE buffer was not shown to disturb normal embryonic development and was recorded the highest survivability to the late tadpole stage (Stage 43); however, injection of increased concentrations of DNA than above provoked irregular cleavages or abnormal appearances, which resulted in reduced survivability. When the injected embryos were incubated at low temperatures (e.g., $12^{\circ}C$), 54.5% of the embryos developed to Stage 43, whereas 42.4% survived when incubated at room temperature. The survivability showed also differences according to the injection site. 58.0% of the embryos developed to Stage 43 when microinjected into the vegetal pole, whereas 44.9% survived when microinjected into the animal pole. To understand the structural fate or behavior of injected DNA a combined light and electron microscopical study was applied. The nucleus-like structure was observed in the ${\lambda}$ DNA-injected embryos, which was quite a similar to the interphase nuclei of normal Xenopus laevis. The nucleus-like structure showed the typical double-layered nuclear membrane and nuclear complexes; however, it consisted of unusual structures such as furrows of nuclear envelope into the nucleoplasm.

• 한국지반신소재학회논문집
• /
• 제12권1호
• /
• pp.51-61
• /
• 2013

본 논문에서는 지오텍스타일 공극 크기 분포를 이미지 분석방법을 이용하여 정량적으로 산출하였다. 연구과정은 실내시험을 통해 지오텍스타일-지오멤브레인 층으로 된 재료를 에폭시 레진으로 포화시킨 후, 양생, 절단하여 그 표면을 디지털 광학현미경으로 관찰하고 정량화함으로 이루어졌다. 여기서는 재료공학에서 주로 사용하는 공간학(stereology)의 개념을 사용하였으며, 지오텍스타일 필라멘트에 의해 둘러싸인 공극의 크기를 최대내접공극크기분포(LIOS)로 표현하였다. 지오텍스타일 내부 축적빈도 50%에 해당하는 공극직경이 압축응력이 10kPa에서 300kPa로 증가함에 따라 $45{\mu}m$가량 감소하였으며, 다시 압축응력을 10kPa로 되돌렸을 경우 초기치의 90%정도 수준으로 회복하였다. 마찰형 지오멤브레인 표면에서 연직응력 100, 300 kPa을 받으며 전단되었을 경우 평균 공극의 크기가 각가 32, 16.5% 감소하였다. 본 논문의 시험 및 분석 결과는 지오텍스타일 내부의 최대내접공극 크기분포가 표면거칠기가 다른 지오멤브레인 표면에서 압축 및 인터페이스 전단됨에 따라 어떻게 변화하는지를 보여준다.

• Elastomers and Composites
• /
• 제44권4호
• /
• pp.455-465
• /
• 2009

본 연구에서는 층상실리케이트에 Octylamine(OA), Dodecylamine(DA), Dimethyldodecylamine(DDA), Octadecylamine(ODA)와 같은 아민류을 사용하여 Organo-montmorillonite(MMT)를 합성한 후 Natural Rubber(NR)와 혼합하여 NR/MMT 나노복합체를 제조하였다. Organo-MMT 및 NR/MMT 나노복합체의 층간거리는 XRD를 사용하여 측정하였으며 NR/MMT 나노복합체의 모폴로지는 SEM을 통하여 관찰하였다. Organo-MMT의 구조분석은 FT-IR을 사용하였다. NR/MMT 나노복합체의 표면 자유에너지, 가황특성, 인장강도, 모듈러스 및 경도는 Contact angle meter, ODR, UTM 및 경도계로 관찰하였다. FT-IR 구조분석으로 MMT 층간에 알킬암모늄 이온의 도입을 확인하였다. 스코치 시간과 적정 가황 시간은 Organo-MMT를 사용한 경우에 단축되었다. NR/DDA-MMT 나노복합체의 표면 자유에너지와 인장강도가 가장 컸다. NR/ODA-MMT 나노복합체의 경도는 가장 컸다.

• 한국세라믹학회지
• /
• 제38권11호
• /
• pp.962-966
• /
• 2001

Crystal structure of PbBi$_2$Nb$_2$$O_{9}$ and $Sr_{1.2}$$Bi_{1.8}$Ta$_2$$O_{9}$ were determined by Rietveld method using neutron diffraction data in the temperature range of 300 K~1273K. Phase transition temperature were measured from the dielectric permittivitytemperature curve. The PbBi$_2$Nb$_2$$O_{9}$ showed a phase transition at about 810 K. In the Sr-excess compound $Sr_{1.2}$$Bi_{1.8}$Ta$_2$$O_{9}$ the phase transition was suppressed down to room temperature. Several structural models were tested by the Rietiveld refinement. Based on the \`R\` values and the structural parameters, the B2cb model is judged to be the most feasible one for the high temperature phase at above 810 K of the PbBi$_2$Nb$_2$$O_{9}$. The $Sr_{1.2}$$Bi_{1.8}$Ta$_2$$O_{9}$ sample was refined to show the most reliable results by the Am2m model.sults by the Am2m model.

• 전자공학회논문지D
• /
• 제35D권3호
• /
• pp.39-45
• /
• 1998

SrBi$_{2}$Ta$_{2}$O$_{9}$ (SBT) ferroelectric thin films for nonvolatile memory were prepared on Pt/Ti/SiO$_{2}$/Si and RuO$_{2}$/SiO$_{2}$/Si substrates by RF magnetron sputtering. The dependences of crystalline and electrical properties on the lower electrode type(Pt and RuO$_{2}$) and the annealing temperatures were investigated. SBT films regardless of their electrode types showed typeical Bi layered peroviskite crystal structures. The crystalline quality of as-deposited SBT films was improved by the rapid thermal annealing at 650.deg. C for 30 sec. The remanetn polarization of 2Pr (Pr+-Pr-) of the annealed SBT films deposited on Pt/Ti/SiO$_{2}$/Si substrates were about 11 .mu.C/cm$^{2}$ and 3 .mu.C/cm$^{2}$, respectively. The leakage currents at 3 V bias voltage were about 0.8 .mu.A/cm$^{2}$ for SBT/ Pt/Ti/SiO$_{2}$/Si and about 1 .mu.A/cm$^{2}$ for SBT/RuO$_{2}$/SiO$_{2}$/Si sample. SBT films annealed at 650 .deg. C showed no degradation in Pr values after 10$^{11}$ polarization switching cycles, indicating good fatigue properties. In addition, for SBT samples deposited on Pt/Ti/SiO$_{2}$/Si, Pr values increased to more than that of initial state, suggesting the increament of leakage current caused by repeated polarization.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2008년도 추계 학술발표회
• /
• pp.860-868
• /
• 2008

Seismic safety analysis of rockfill dams are consist of the stability analysis as an simplifed method and the dynamic analysis as an detailed method. When high risk dams such as Multi-purpose dams were often applied detailed method by dynamic analysis, dynamic properties of dam materials such as shear modulus are considered as most important factor. Dynamic material properties such as shear modulus had to be investigated by cyclic triaxial test et al. during design and construction stage but these were not conducted because of the condition of domestic seismic design technique. MASW and SASW methods had been applied as a non destructive method to investigate dynamic material properties of existing rockfill dam, has no problems in dam safety at present. These methods were usually performed under the assumptions that the subsurface can be described horizontally homogeneous and isotropic layers. Recent studies(Marwin, 1993, Kim, 2001) showed that surface waves generated through inclined structures have different characteristics from those through a horizontally homogeneous layered model. further Kim et al(2005) and Min and Kim(2006) showed that central core type rockfill dam overestimated the shear wave velocities as increasing the depth through the 3D numerical modelling dut to the effect of outer rockfill and geometrical reasons In this study the results of shear wave velocities of seven rockfill dams form comprehensive facility review, was carried out from 2003 to 2007, were collected and analysed to establish the shear wave velocity distribution characteristics in increasing confining stress in rockfill dams and surface wave velocity ranges in rockfill dam through MASW and the limitation in application are discussed to be utilized as an reference value for dynamic analysis.