京畿道의 植物相 : 태화산, 화야산, 대부도, 칠현산, 철마산, 검단산

崔道烈,張珍成,金正猷,全正壹,金輝,閔雄基,姜佑昌 서울대학교 수목원 2001 서울大學校 樹木園 硏究報告 Vol.- No.21

This study was conducted in order to explore general flora of the Gyounggi-do Province and to clarify the distribution of some specificated taxa of the Korea. Daebu-do Island, Mt. Taewha, Mt. Hwaya, Mt. Gumdan, Mt. Chilhyun and Mt. Chulma among eighth grade-area of the Degree of Green Naturality (DGN) within the boundary of the Gyounggi-do Province were visited to investigate local flora. The number of identified vascular plant species were as follow; Mt. Hwaya: 120 species (99 genera of 67 families), Mt. Teawha: 132 species (103 genera of 56 families), Daebu-do Island: 124 species (103 genera of 50 families), Mt. Chulma: 129 species (99 genera of 67 families), Mt. Gumdan: 121 species (96 genera of 52 families), Mt. Chilyun: 90 species (74 genera of 42 families). The endemic Clematis brachyura Maxim. was found to distribute Daeby-do. It seemed that plantation was occupying large area in forest of the Gyounggi-do Province. Forty two specificated taxa were identified and 3 taxa, 10 taxa, 5 taxa, and 24 taxa were sorted into forth grade, third grade, second grade, and first grade respectively. Mt. Taewha showed the highest record (16 taxa) in the number of specificated taxa, Mt. Hwaya was the next with 13 taxa. Mt, Chulma (12 taxa), Mt. Gumdan (11 taxa), Daebu-do Island (7 taxi), and Mt, Chylma (4 taxi) followed. Mt. Taewa and Mt. Whaya were found to be relatively higher in the score calculated front the specificated taxa distribution, while Daebu-do Island and Mt. Chilyun were lower, that difference was probably due in part to consequences of severe disturbance of human activities. With respect to the consequences of severe disturbance of human activities. With respect to the geographical proximity to the Gangwon Province, Mt. Hwaya showed higher similarity of the species composition to that of the Mt. Jumbong.

大岩山의 植物相

閔雄基,張珍成,全正壹,金輝,崔道烈,鄭承洙 서울대학교 수목원 2000 서울大學校 樹木園 硏究報告 Vol.- No.20

This study was carried out to investigate the flora of Mts. Dae-am, Dae-woo, Baek-suk, and Sa-myung located on the east side of DMZ in province Yang-gu-gun, from July 1999 to August 2000. Although two hundred and fifty eight vascular plant taxa (70 families 167 genera) were recorded, this was only a part of representatives in this community because of the restrictin of collections within the military zone. The overall forest stand age of this area was 40 to 50 years, but occasionally ca 70 years old trees were found. We reported 11 taxa of the rare and endangered species proposed by the Ministry of Environment in this area. The Yong-neup, the only high altitude (alt. 1,200m) moore in south Korea, are located in the peak of Mt. Dae-am-san. Some species of this moore (Carex chordorrhiza Ehrh., Carex limosa L., and Gentiana jamesii Hemsl.) - were only found in south Korea. This moor would suffer vegetation change by natural moorland succession and human disturbances. The long-term monitoring of variation of annual vegetation, species distribution, numbers and distribution pattern of individuals of rare species are recommended for the wetland conservation.

단조해석을 위한 직접 행렬해법에 대한 일반적 비교

박용복,안병기,김정호,양동열 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.1

유한요소해석이 소성가공 공정설계를 위하여 사용되어져 왔다. 유한요소해석은 단조공정 을 이해하기 위해서 더욱 중요해질 것이다. 복잡한 단조해석을 수행하기 위해서는 적절한 행렬해법의 제시가 해석 기법의 전반적인 효율성을 위하여 매우 중요하다. 문제 크기가 커짐에 따라 유한요소 모델과 관계한 대수방정식 해를 푸는데 소요되는 계산시간의 효율적인 처리가 필요하다. 많은 행렬기법이 개발되어져 왔고 본 논문은 이러한 목적을 위하여 멀티프란틀 해법을 제안한다. FEA(Finite Element Analysis) has been used for metal forming process design. FEA will become more and more important in understanding forging process. For large-scale forging analysis problems. the performance of a linear equation solver is very important for the overall efficiency of the analysis code. With problem size increased. the computation time needs to be reduced, which is spent on solving the system of algebraic equations associated with finite element model. Many matrix solvers have been developed and the paper has proposed multifrontal solver for this purpose.

雲達山의 植物相

閔雄基,張珍成,全正壹,金輝,崔道烈,金承昆 서울대학교 수목원 2001 서울大學校 樹木園 硏究報告 Vol.- No.21

This study was carried out to investigate the flora of Mt. Undal (alt. 1,097.2m) located on the northwestern side of province Gyeongsangbuk-do, near Myngyeong-si city, from April 2000 to Sept. 2000. Total number of vascular plants discovered in Mt. Undal were 70 families, 154 genera, and 243 taxa(including species, subspecies, varieties and forma). Major vegetation was Acer pictum var. mono - Quercus mongolica - Carpinus laxiflora community. The overall forest stand age of this area was 40 to 50 years, and occasionally ca 70 years old Abies holophylla trees were found. Although, there were no rare and endangered speices, we found two species of level IV by the Ministry of Environment - Anemone koraiensis Nakai, Anemone reflexa. Steph. et Willd.

All‐Carbon Nanotube‐Based Flexible Field‐Emission Devices: From Cathode to Anode

Jeong, Hee Jin,Jeong, Hae Deuk,Kim, Ho Young,Kim, Jun Suk,Jeong, Seung Yol,Han, Joong Tark,Bang, Dae Suk,Lee, Geon‐,Woong WILEY‐VCH Verlag 2011 Advanced functional materials Vol.21 No.8

<P><B>Abstract</B></P><P>The fabrication of a flexible field‐emission device (FED) using single‐walled carbon nanotube (SWNT) network films as the conducting electrodes (anode and cathode) and thin multi‐walled CNT/TEOS hybrid films as the emitters is reported. P‐type doping with gold ions and passivation with tetraethylorthosilicate (TEOS) made the SWNT network film highly conductive and environmentally stable, and hence a good alternative to conventional indium tin oxide electrodes. CNT/TEOS hybrid emitters showed high current density, low turn‐on field, and long‐term emission stability, compared with CNT emitters; these characteristics can be attributed to the TEOS sol, acting both as a protective layer surrounding the nanotube tip, and as an adhesive layer enhancing the nanotube adhesion to the substrate. All‐CNT‐based flexible FEDs fabricated by this approach showed high flexibility in field emission characteristics and extremely bright electron emission patterns.</P>

Arrays of vertically aligned tubular-structured graphene for flexible field emitters

Jeong, Hee Jin,Kim, Ho Young,Jeong, Hae Deuk,Jeong, Seung Yol,Han, Joong Tark,Lee, Geon-Woong The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.22

<P>Arrays of tubular-structured reduced graphene oxide (RGO) were fabricated by a simple method involving filtration of a solution containing highly dispersed RGO sheets. The length and alignment of the tubular-structured RGO arrays were controlled by the filtration rate and by tuning the interactions between the hydrophobic RGO sheets and the porous walls, rather than the top surfaces, of the polycarbonate filter membrane. As expected, the lengths of the RGO arrays increased with higher filtration rates; however, maximum field emission characteristics were obtained at an intermediate filtration rate because field screening reduced electron emission from the longer-length RGO arrays. ZnO-coated RGO arrays showed excellent emission stability without significant current degradation or fluctuations, even under O<SUB>2</SUB> exposure. The ZnO layer protected the emission site of the RGO arrays from the reactive ion bombardment of oxidative gas species. Moreover, the RGO arrays were highly flexible with preservation of the field emission properties, even at large bending angles. The excellent field emission characteristics of the tubular structured RGO arrays were attributed to the high crystallinity, abundant sharp edges, and the chemical stability of the RGO arrays, as well as the strong interactions between the RGO arrays and the substrate.</P> <P>Graphic Abstract</P><P>High-performance flexible field emission was demonstrated using tubular-structured reduced graphene oxide arrays by a simple method involving filtration of a solution containing highly dispersed RGO sheets. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm31263h'> </P>

Chirality-specific transport phenomena of isolated single-walled carbon nanotube

Jeong, Seung Yol,Perello, David,Kim, Sung Jin,Jang, Jin Ho,Kang, Bo Ram,Yu, Woo Jong,Bae, Dong Jae,Yun, Minhee,Lee, Young Hee WILEY-VCH Verlag 2007 Physica Status Solidi. B Vol.244 No.11

<P>Single-walled carbon nanotube-field effect transistors (SWCNT-FETs) have been fabricated using in-situ thermal chemical vapor deposition. For isolated devices, the resonant Raman spectra confirmed that the full width at half maximum (FWHM) of the radial breathing mode (RBM) peaks was about 4 cm<SUP>–1</SUP>, consistent with atomic force microscopy (AFM) images that clearly revealed the individually isolated SWCNTs on the patterned substrate with a diameter of 1.3 nm. Subsequent I –V measurements of the SWCNT-FET revealed a clear gating effect for samples with semiconducting SWCNTs. The transport phenomena of a device with mixed metallic and semiconducting SWCNTs network were governed by the metallic nanotube with severely suppressed gate modulation. Identification of the chirality of SWCNTs by resonant Raman spectroscopy prior to the I –V characteristics guarantees the validity of working FET devices. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

One-step transfer and integration of multifunctionality in CVD graphene by TiO2/graphene oxide hybrid layer.

Jeong, Hee Jin,Kim, Ho Young,Jeong, Hyun,Han, Joong Tark,Jeong, Seung Yol,Baeg, Kang-Jun,Jeong, Mun Seok,Lee, Geon-Woong Wiley-VCH 2014 Small Vol.10 No.10

<P>We present a straightforward method for simultaneously enhancing the electrical conductivity, environmental stability, and photocatalytic properties of graphene films through one-step transfer of CVD graphene and integration by introducing TiO2/graphene oxide layer. A highly durable and flexible TiO2 layer is successfully used as a supporting layer for graphene transfer instead of the commonly used PMMA. Transferred graphene/TiO2 film is directly used for measuring the carrier transport and optoelectronic properties without an extra TiO2 removal and following deposition steps for multifunctional integration into devices because the thin TiO2 layer is optically transparent and electrically semiconducting. Moreover, the TiO2 layer induces charge screening by electrostatically interacting with the residual oxygen moieties on graphene, which are charge scattering centers, resulting in a reduced current hysteresis. Adsorption of water and other chemical molecules onto the graphene surface is also prevented by the passivating TiO2 layer, resulting in the long term environmental stability of the graphene under high temperature and humidity. In addition, the graphene/TiO2 film shows effectively enhanced photocatalytic properties because of the increase in the transport efficiency of the photogenerated electrons due to the decrease in the injection barrier formed at the interface between the F-doped tin oxide and TiO2 layers.</P>

A 5-year retrospective clinical study of the Dentium implants

Jeong-Yol Lee,Hyo-Jin Park,Jong-Eun Kim,Yong-Geun Choi,Young-Soo Kim,Jung-Bo Huh,Sang-Wan Shin 대한치과보철학회 2011 The Journal of Advanced Prosthodontics Vol.3 No.4

PURPOSE The aim of this retrospective study was to evaluate cumulative survival rate (CSR) of Implantium implants followed for 5 years and association between risk factors and the CSR. MATERIALS AND METHODS A total of two hundred forty-nine Implantium Implants System (Dentium, Seoul, Korea) placed in ninety-five patients from 2004 to 2009 were investigated with several identified risk factors (sex, systemic disease, smoking, alchohol, reason of tooth loss, length, arch (maxilla or mandible), replace tooth type (incisor, canine, premolar or molar) Kennedy classification, prosthodontic type, prosthodontic design, opposite dentition, abutment type, occlusal material, occlusal unit, splint to tooth, cantilever, other surgery). Clinical examination (mobility, percussion, screw loosening, discomfort, etc.) and radiographic examination data were collected from patient records including all problems during follow-up period according to protocols described earlier. Life table analysis was undertaken to examine the CSR. Cox regression method was conducted to assess the association between potential risk factors and overall CSR. RESULTS Five of 249 implants were failed. Four of these were lost before loading. The 5-year implant cumulative survival rate was 97.37%. Cox regression analysis demonstrated a significant predictive association between overall CSR and systemic disease, smoking, reason of tooth loss, arch, Kennedy classification and prosthodontic design (P<.05). The screw related complication was rare. Two abutment screw fractures were found. Another complications of prosthetic components were porcelain fracture, resin facing fracture and denture fracture (n=19). CONCLUSION The 5-year CSR of Implantium implants was 97.37%. Implant survival may be dependent upon systemic disease, smoking reason of tooth loss, arch, Kennedy classification and prosthodontic design (P<.05). The presence of systemic diseases and combination of other surgical procedures may be associated with increased implant failure.

Highly Concentrated and Conductive Reduced Graphene Oxide Nanosheets by Monovalent Cation–<i>π</i> Interaction: Toward Printed Electronics

Jeong, Seung Yol,Kim, Sung Hun,Han, Joong Tark,Jeong, Hee Jin,Jeong, Soo Yeon,Lee, Geon‐,Woong WILEY‐VCH Verlag 2012 Advanced Functional Materials Vol.22 No.15

<P><B>Abstract</B></P><P>A novel route to preparing highly concentrated and conductive reduced graphene oxide (RGO) in various solvents by monovalent cation–<I>π</I> interaction. Previously, the hydrophobic properties of high‐quality RGO containing few defects and oxygen moieties have precluded the formation of stable dispersion in various solvents. Cation–<I>π</I> interaction between monovalent cations, such as Na<SUP>+</SUP> or K<SUP>+</SUP>, and six‐membered sp<SUP>2</SUP> carbons on graphene were achieved by simple aging process of graphene oxide (GO) nanosheets dispersed in alkali solvent. The noncovalent binding forces introduced by the cation–<I>π</I> interactions were evident from the chemical shift of the sp<SUP>2</SUP> peak in the solid <SUP>13</SUP>C NMR spectra. Raman spectra and the <I>I</I>‐<I>V</I> characteristics demonstrated the interactions in terms of the presence of <I>n</I>‐type doping effect due to the adsorption of cations with high electron mobility (39 cm<SUP>2</SUP>/Vs). The RGO film prepared without a post‐annealing process displayed superior electrical conductivity of 97,500 S/m at a thickness of 1.7 μm. Moreover, mass production of GO paste with a concentration as high as 20 g/L was achieved by accelerating the cation–<I>π</I> interactions with densification process. This strategy can facilitate the development of large scalable production methods for preparing printed electronics made from high‐quality RGO nanosheets.</P>