• Title/Summary/Keyword: Critical factor

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N- and P-doping of Transition Metal Dichalcogenide (TMD) using Artificially Designed DNA with Lanthanide and Metal Ions

  • Kang, Dong-Ho;Park, Jin-Hong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.292-292
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    • 2016
  • Transition metal dichalcogenides (TMDs) with a two-dimensional layered structure have been considered highly promising materials for next-generation flexible, wearable, stretchable and transparent devices due to their unique physical, electrical and optical properties. Recent studies on TMD devices have focused on developing a suitable doping technique because precise control of the threshold voltage ($V_{TH}$) and the number of tightly-bound trions are required to achieve high performance electronic and optoelectronic devices, respectively. In particular, it is critical to develop an ultra-low level doping technique for the proper design and optimization of TMD-based devices because high level doping (about $10^{12}cm^{-2}$) causes TMD to act as a near-metallic layer. However, it is difficult to apply an ion implantation technique to TMD materials due to crystal damage that occurs during the implantation process. Although safe doping techniques have recently been developed, most of the previous TMD doping techniques presented very high doping levels of ${\sim}10^{12}cm^{-2}$. Recently, low-level n- and p-doping of TMD materials was achieved using cesium carbonate ($Cs_2CO_3$), octadecyltrichlorosilane (OTS), and M-DNA, but further studies are needed to reduce the doping level down to an intrinsic level. Here, we propose a novel DNA-based doping method on $MoS_2$ and $WSe_2$ films, which enables ultra-low n- and p-doping control and allows for proper adjustments in device performance. This is achieved by selecting and/or combining different types of divalent metal and trivalent lanthanide (Ln) ions on DNA nanostructures. The available n-doping range (${\Delta}n$) on the $MoS_2$ by Ln-DNA (DNA functionalized by trivalent Ln ions) is between $6{\times}10^9cm^{-2}$ and $2.6{\times}10^{10}cm^{-2}$, which is even lower than that provided by pristine DNA (${\sim}6.4{\times}10^{10}cm^{-2}$). The p-doping change (${\Delta}p$) on $WSe_2$ by Ln-DNA is adjusted between $-1.0{\times}10^{10}cm^{-2}$ and $-2.4{\times}10^{10}cm^{-2}$. In the case of Co-DNA (DNA functionalized by both divalent metal and trivalent Ln ions) doping where $Eu^{3+}$ or $Gd^{3+}$ ions were incorporated, a light p-doping phenomenon is observed on $MoS_2$ and $WSe_2$ (respectively, negative ${\Delta}n$ below $-9{\times}10^9cm^{-2}$ and positive ${\Delta}p$ above $1.4{\times}10^{10}cm^{-2}$) because the added $Cu^{2+}$ ions probably reduce the strength of negative charges in Ln-DNA. However, a light n-doping phenomenon (positive ${\Delta}n$ above $10^{10}cm^{-2}$ and negative ${\Delta}p$ below $-1.1{\times}10^{10}cm^{-2}$) occurs in the TMD devices doped by Co-DNA with $Tb^{3+}$ or $Er^{3+}$ ions. A significant (factor of ~5) increase in field-effect mobility is also observed on the $MoS_2$ and $WSe_2$ devices, which are, respectively, doped by $Tb^{3+}$-based Co-DNA (n-doping) and $Gd^{3+}$-based Co-DNA (p-doping), due to the reduction of effective electron and hole barrier heights after the doping. In terms of optoelectronic device performance (photoresponsivity and detectivity), the $Tb^{3+}$ or $Er^{3+}$-Co-DNA (n-doping) and the $Eu^{3+}$ or $Gd^{3+}$-Co-DNA (p-doping) improve the $MoS_2$ and $WSe_2$ photodetectors, respectively.

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Development of GIS based Water Quality Simulation System for Han River and Kyeonggi Bay Area (한강과 경기만 지역 GIS 기반 통합수질모의 시스템 개발)

  • Lee, Chol-Young;Kim, Kye-Hyun
    • Journal of Korea Spatial Information System Society
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    • v.10 no.4
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    • pp.77-88
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    • 2008
  • There has been growing demands to manage the water quality of west coastal region due to the large scale urbanization along the coastal zone, the possibility of application of TMDL(Total Maximum Daily Loadings) to Han river, and the natural disaster such as oil spill incident in Taean, Chungnam. However, no system has been developed for such purposes. In this background, the demand of GIS based effective water quality management has been increased to monitor water quality environment and propose best management alternatives for Han river and Kyeonggi bay. This study mainly focused on the development of integrated water quality management system for Han river bas in and its estuary are a connected to Kyeonggi bay to support integrated water quality management and its plan. Integration was made based on GIS by spatial linking between water quality attributes and location information. A GIS DB was built to estimate the amount of generated and discharged water pollutants according to TMDL technical guide and it included input data to use two different water quality models--W ASP7 for Han river and EFDC for coastal area--to forecast water quality and to suggest BMP(Best management Practices). The results of BOD, TN, and TP from WASP7 were used as the input to run EFDC. Based on the study results, some critical areas which have relatively higher pollutant loadings were identified, and it was also identified that the locations discharging water pollutant loadings to river and seasonal factor affected water quality. And the relationship of water quality between river and its estuary area was quantitatively verified. The results showed that GIS based integrated system could be used as a tool for estimating status-quo of water quality and proposing economically effective BMPs to mitigate water pollution. Further studies need to be made for improving system's capabilities such as adding decision making function as well as cost-benefit analysis, etc. Also, the concrete methodology for water quality management using the system need to be developed.

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Influence of the Existing Cavern on the Stability of Adjacent Tunnel Excavation by Small-Scale Model Tests (축소모형시험을 통한 공동이 근접터널 굴착에 미치는 영향평가)

  • Jung, Minchul;Hwang, Jungsoon;Kim, Jongseob;Kim, Seungwook;Baek, Seungcheol
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.12
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    • pp.117-128
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    • 2014
  • Generally, when constructing a tunnel close to existing structures, the tunnel must be built at a constant distance from the structures that is more than width of tunnel to minimize the impact of interference between an existing structures and new tunnel. Spacing of these closed tunnels should be designed considering soil state, size of tunnel and reinforcement method. Particularly when the ground is soft, a care should be taken with the tunnel plans because the closer the tunnel is to the existing structures, the greater the deformation becomes. As methods of reviewing the effect of cavities on the stability of a tunnel, field measurement, numerical analysis and scaled model test can be considered. In the methods, the scaled model test can reproduce the engineering characteristics of a rock in a field condition and the shape of structures using the scale factor even not all conditions cannot be considered. In this study, when construction of a tunnel close to existing structures, the method and considering factors of the scaled model test were studied to predict the actual tunnel behavior in planning stage. Furthermore, model test results were compared with the numerical analysis results for verifying the proposed model test procedure. Also, practical results were derived to verify the stability of a tunnel vis-a-vis cavities through the scaled model test, which assumed spacing distances of 0.25 D, 0.50 D, and 1.00 D between the cavities and tunnel as well as the network state distribution. The spacing distances of 1.0 D is evaluated as the critical distance by the results of model test and numerical analysis.

A New Detailed Assessment for Liquefaction Potential Based on the Liquefaction Driving Effect of the Real Earthquake Motion (실지진하중의 액상화 발생특성에 기초한 액상화 상세평가법)

  • 최재순;강한수;김수일
    • Journal of the Korean Geotechnical Society
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    • v.20 no.5
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    • pp.145-159
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    • 2004
  • The conventional method for assessment of liquefaction potential proposed by Seed and Idriss has been widely used in most countries because of simplicity of tests. Even though various data such as stress, strain, stress path, and excess pore water pressure can be obtained from the dynamic test, especially, two simple experimental data such as the maximum deviatoric stress and the number of cycles at liquefaction have been used in the conventional assessment. In this study, a new detailed assessment for liquefaction potential to reflect both characteristics of real earthquake motion and dynamic soil resistance is proposed and verified. In the assessment, the safety factor of the liquefaction potential at a given depth of a site can be obtained by the ratio of a resistible cumulative plastic shear strain determined through the performance of the conventional cyclic test and a driving cumulative plastic shear strain calculated from the shear strain time history through the ground response analysis. The last point to cumulate the driving plastic shear strain to initiate soil liquefaction is important for this assessment. From the result of cyclic triaxial test using real earthquake motions, it was concluded that liquefaction under the impact-type earthquake loads would initiate as soon as a peak loading signal was reached. The driving cumulative plastic shear strain, therefore, can be determined by adding all plastic shear strains obtained from the ground response analysis up to the peak point. Through the verification of the proposed assessment, it can be concluded that the proposed assessment for liquefaction potential can be a progressive method to reflect both characteristics of the unique soil resistance and earthquake parameters such as peak earthquake signal, significant duration time, earthquake loading type, and magnitude.

Effect of Different Wind-break Net on Reducing Damage of Cold Sea Wind (수도 풍해경감을 위한 방풍강 강목의 효과)

  • 이승필;김상경;이광석;최대웅;김칠용
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.35 no.4
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    • pp.352-361
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    • 1990
  • The reducing effect of wind injury was investigated using several wind-break nets in Youngdeok province where cold-wind damage is often occurred during rice growing season. The white-head damage of rice have been often occurred by typhoon during the period between August 15 to September 10 in the cold wind area of the eastern coastal during the last 11 years (1979-1989). This may suggest that the critical period for heading will be by August 15 in the regions. High evaporation coefficient, more than 250 due to typhoon passage over the regions resulted high injury of white head. Generally, the wind injury have been caused by warm and dry westerlies through Fohn apperance in Taebaeg mountains and by cool-humid wind which blows from coast to inland. The frequency of occurrence of the two types of typhoons were 25, 20%, respectively during rice cultivation. The instalation of wind-break net significantly reduced the wind blowing speed, depending on the net mesher with the higher effect in dence net. The distances between the net and cropping area also affect the wind speed: 23% reduction at 1m distance. 34% at 10m and 28% at 20m, respectively. The reducing effect was also observed even at 10 times height of the wind-break net. The instalation of wind-break net gave several effects on climate factor, showing that temperature increased by 0.8$^{\circ}C$(maximum), 0.7$^{\circ}C$(minimum), 0.6$^{\circ}C$(average) : water temperatures increased by 0.5$^{\circ}C$(maximum), 0.6$^{\circ}C$(minimum), 0.5$^{\circ}C$(average) : soil temperature increased 0.4$^{\circ}C$. The earlier heading and increasing growth rate, use of light, culm length, panicle number per hill, spikelet number per panicle, fertility and 1,000 grain weight were observed in the fields with the wind-break nets resulting in 10-15% increase in rice yield using 0.5${\times}$0.5cm nets. The increasing seedlings per hill gave higher grain yield by 13% in the cold wind damage regions of eastern coastals. and the wind-break was more significant in the field without the wind-break net. Wind injury of rice plant in the cold wind regions of eastern coastals in korea could be reduced by selection of tolerant varieties to wind injury, adjustment of transplanting time, and establishment of wind-break nets.

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Flavonoid Profiles of Quercus mongolica Fisch. ex Ledeb. and Q. serrata Murray (Fagaceae) in Mt. Seorak, Korea: Taxonomical and Ecological Implications (설악산 신갈나무와 졸참나무의 플라보노이드 조성과 분류학적, 생태학적 의미)

  • Park, Jin Hee
    • Journal of Life Science
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    • v.24 no.10
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    • pp.1092-1101
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    • 2014
  • In this study, the distribution patterns of Quercus mongolica and Q. serrata in Korea were investigated, and the possibility of introgressive hybridization and gene flow between Q. mongolica and Q. serrata in Mt. Seorak was inferred by flavonoid analyses. The most critical factor in the vertical and horizontal distribution patterns of Q. mongolica and Q. serrata was the temperature, in accordance with latitude and altitude. The species showed a zonal distribution, with a Q. mongolica zone in the upper area and a Q. serrata zone in the lower area. In Mt. Seorak, Central Korea, the range of the vertical distribution of Q. mongolica was generally above an altitude of 100 m, whereas that of Q. serrata was an altitude of 0-400 m (-500) and rarely above an altitude of 500 m. However, in Mt. Jiri, Southern Korea, Q. serrata was found up to an altitude of 1,000~1,200 m, whereas the frequency of Q. mongolica was reduced at lower elevations and the species was rare below an altitude of 300 m, although pure stands were found on higher mountain slopes above an altitude of 1,200 m. The altitudinal distribution of the two species overlapped, where the two species occurred together. The leaf flavonoid constituents of thirty-four individuals of Q. mongolica and Q. serrata in Mt. Seorak and Mt. Jiri, Korea were examined. Twenty-four flavonoid compounds were isolated and identified. These were glycosylated derivatives of flavonols kaempferol, quercetin, isorhamnetin, myricetin. Five compounds among the flavonoid compounds were acylated. Kaempferol 3-O-glucoside, quercetin 3-O-glucoside, quercetin 3-O-galactoside, and its acylated compounds were major constituents and present in all individuals. Quercus mongolica is distinguished from Q. serrata by the presence of quercetin 3-O-arabinosylglucoside, a high concentration of three acylated compounds (kaempferol 3-O-glucoside, quercetin 3-O-glucoside, and quercetin 3-O-galactoside), and a relatively low concentration or lack of rhamnosyl flavonol compounds. Intraspecific variations, however, were found in the flavonoid profiles of Q. mongolica and Q. serrata, and the flavonoid profiles of individuals belonging to the two species in a hybrid zone (sympatric zone) tended to be similar, qualitatively and quantitatively. These findings strongly suggest that gene exchange or gene flow occurs through introgressive hybridization between Q. mongolica and Q. serrata in Mt. Seorak.

Quantitative Microbial Risk Assessment Model for Staphylococcus aureus in Kimbab (김밥에서의 Staphylococcus aureus에 대한 정량적 미생물위해평가 모델 개발)

  • Bahk, Gyung-Jin;Oh, Deog-Hwan;Ha, Sang-Do;Park, Ki-Hwan;Joung, Myung-Sub;Chun, Suk-Jo;Park, Jong-Seok;Woo, Gun-Jo;Hong, Chong-Hae
    • Korean Journal of Food Science and Technology
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    • v.37 no.3
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    • pp.484-491
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    • 2005
  • Quantitative microbial risk assessment (QMRA) analyzes potential hazard of microorganisms on public health and offers structured approach to assess risks associated with microorganisms in foods. This paper addresses specific risk management questions associated with Staphylococcus aureus in kimbab and improvement and dissemination of QMRA methodology, QMRA model was developed by constructing four nodes from retail to table pathway. Predictive microbial growth model and survey data were combined with probabilistic modeling to simulate levels of S. aureus in kimbab at time of consumption, Due to lack of dose-response models, final level of S. aureus in kimbeb was used as proxy for potential hazard level, based on which possibility of contamination over this level and consumption level of S. aureus through kimbab were estimated as 30.7% and 3.67 log cfu/g, respectively. Regression sensitivity results showed time-temperature during storage at selling was the most significant factor. These results suggested temperature control under $10^{\circ}C$ was critical control point for kimbab production to prevent growth of S. aureus and showed QMRA was useful for evaluation of factors influencing potential risk and could be applied directly to risk management.

The influences of individual personality types on ERP system's acceptance: a preliminary test (개인의 성격유형이 ERP수용에 미치는 영향에 관한 탐색적 연구)

  • Kim, Hyun-Sang;Lee, Jang-Hyung
    • Journal of Korea Society of Industrial Information Systems
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    • v.11 no.4
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    • pp.47-65
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    • 2006
  • The application of the ERP system is becoming more common to the businesses since a firm needs to reinforce positive competitiveness and to maintain competitive advantage. The ERP system is an enterprise integration solution that converts the whole business processes through information technology. Extant research provides plenty of results about the success factors of the ERP system; however, most of the researches focus on the exterior factors such as techniques rather than on the influences that a firm's employees' individual personality has in accepting the information technology of the ERP system. The objective of this study is to investigate the role of the employees' individual personality as a factor that makes the ERP system a success. The surveys--composed of the extent of information technology acceptance about the personality type of MBTI (Myers-Briggs type indicator) and the ERP system--were given to the companies applying the ERP system The personality type of MBTI is measured by 4 types of Myers, and Davis's TAM (technology acceptance model) is used for the information technology acceptance. The results of this study are summarized as follows. First the extraversion and the judging in the personality types of MBTI have a significant influence on the information technology acceptance of the ERP system. However, the thinking and the feeling in the personality types of MBTI were analyzed to not have a critical affect on the ERP system acceptance. Second as verified in the extant research the information technology acceptance verification related to the ERP system has a significant influence on perceived ease of use, perceived usefulness, behavioral intention and actual usage of the ERP system. The results of this study can be used for a successful application of the ERP system as follows. First it offers foundation of perception that the type of the individual personality is a significant key figure for the successful use of the ERP system. Second it provides a basis for the knowledge of combining the model of information technology acceptance and the psychological factors.

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Development of Practical Problem-focused teaching plans for Teenagers' 'Preparation for Successful aging' in the 'Family life in old age' unit (고등학생의 '성공적인 노후생활 준비교육'을 위한 실천적 문제 중심 가정과 수업의 교수 설계와 개발)

  • Lee, Jong-Hui;Cho, Byung-Eun
    • Journal of Korean Home Economics Education Association
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    • v.23 no.3
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    • pp.161-183
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    • 2011
  • This study aims to design, develop the impact of a high school course in practical problem- focused teaching plan which will enable students to deal with an aging society, and prepare well for the aging by looking at issues the elderly face. This study set a target of analyzing the 2007 revised curriculum manual to develop instructor-led teaching and learning plans for 'Successful aging preparation'. Five common subjects were reframed on a practical problem basis through factor analysis of preliminary research regarding aging education for teenagers and the 2007 revised curriculum and textbooks of Technology Home Economics, and Human Development. The practical problem was 'What do we need to do to Successfully live an independent life in aging?', and the subjects studied to answer this question were the aging society and population changes. the nature of the elderly, aging preparation, care of the elderly, and welfare services for the elderly. These five subjects were grouped under the main categories of The Aging Society. Understanding the Elderly, and aging Preparation. The ultimate objective of the lessons was, through critical reasoning, to inquire into the causes of current problems the elderly face so that teenagers can understand aging societies and the elderly, and prepare for a Successful aging. Another objective was to seek reasonable alternatives for teenagers as they prepare for Successful and independent aging, and increase their problem-solving abilities in choosing the best course of action by considering the ripple effect of consequences of each of those alternatives. The practical problem-teaching lesson plans consisted of five classes on practical reasoning instruction. This study suggests that new high school curricula should include lessons on preparation for aging so that students can deal successfully with our aging society.

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The effect of screw tightening techniques on the detorque value in internal connection implant superstructure (내부연결 임플란트 상부구조물에서 나사조임술식이 풀림토크값에 미치는 영향)

  • Choi, Jung-Han
    • The Journal of Korean Academy of Prosthodontics
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    • v.48 no.4
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    • pp.243-250
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    • 2010
  • Purpose: This study evaluated the effect of different screw tightening sequences and methods on detorque values in a well-fitting implant superstructure. Materials and methods: A fully edentulous mandibular master model and a metal framework directly connected to four parallel implants (Astra Tech) with a passive fit to each other were fabricated. Six stone casts were made with a splinted impression technique to represent a 'well-fitting' situation with the metal framework. Detorque values were measured twice after screw tightening using 20 Ncm. Detorque values and minimum detorque values for three screw tightening sequences (1-2-3-4, 2-4-3-1, and 2-3-1-4) and for two tightening methods (two-step and one-step) were analyzed using multi-way analysis of variance and two-way analysis of variance, respectively, at a .05 level of significance. Results: The mean detorque values for screw tightening sequences ranged from 12.8 Ncm (2-4-3-1) to 13.1 Ncm (2-3-1-4), and for screw tightening methods were 13.1 Ncm (two-step) and 11.8 Ncm (one-step). The mean of mimimum detorque values for screw tightening sequences were 11.1 Ncm (1-2-3-4) and 11.2 Ncm (2-4-3-1 and 2-3-1-4), and for screw tightening methods were 11.2 Ncm (two-step) and 9.9 Ncm (one-step). No statistically significant differences among three screw tightening sequences were found for detorque values and for mimimum detorque values. But, statistically significant differences between two screw tightening methods were found for two values. Two-step screw tightening method showed higher detorque value (P = .0003) and higher minimum detorque value (P = .0035) than one-step method. Conclusion: Within the limitations of this study, the screw tightening sequence was not a critical factor for the detorque values in a well-fitting implant superstructure by the splinted impression technique. But, two-step screw tightening method showed greater detorque values than one-step method.