• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.2
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• pp.78-81
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• 2020

Quantum dot efficiency was increased to evaluate reliability and optical characteristics using incidental materials. Quantum dot was manufactured by wrapping a sandwich type quantum layer using a product with a barrier property to prevent water and oxygen because it is vulnerable to oxygen and moisture. We used the three quantum dot films consisting of quantum dot only and quantum dot products consisting of film and barrier film combined with PET in the quantum dot product to evaluate the change over 650 hours under high temperature and high humidity conditions at 60℃ and 90 % humidity. As a result, the quantum dot product with Barrier Film has lowered luminance by 8 %, CIE x by 2 % and CIE y by 8 %. Quantum dot products exposed to moisture and oxygen were oxidized and measured low before measurement.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.509-514
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• 2005

In recent years, use of the web technologies and on-line process has immensely swapped single-user platform practice. This study attempted to develop preliminary cost estimating program by means of Web technologies based on statistical modeling results. A prototype Web-based Preliminary Item-Level Cost Estimating System (WBPILCES) using open source software was developed as an on-line estimating tool in this research. The primary objective is to study the possible flexibility of implementing a centralized information system that will be maintained by the Texas Department of Transportation (TxDOT) IT division. The full-scale deployment of proposed information architecture is expected to seamlessly integrate with legacy database system currently used by TxDOT so as to streamline data storage, cost growth tracking and estimates documentation.

• Journal of Institute of Convergence Technology
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• v.4 no.1
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• pp.21-27
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• 2014

White LEDs (light-emitting diodes) are promising new-generation light sources which can replace conventional lamps due to their high reliability, low energy consumption and eco-friendly effects. This paper briefly reviews recent progress of oxy/nitride host phosphor and quantum dot materials with broad excitation band characteristics for phosphor-converted white LEDs. Among oxy/nitride host materials, $M_2Si_5N_8:Eu^{2+}$, $MAlSiN_3:Eu^{2+}$ M-SiON(M=Ca, Sr, Ba), ${\alpha}/{\beta}-SiAlON:Eu^{2+}$ are excellent phosphors for white LED using blue-emitting chip. They have very broad excitation bands in the range of 440-460 nm and exhibit emission from green to red. In this paper, In this review we focus on recent developments in the crystal structure, luminescence and applications of the oxy/nitride phosphors for white LEDs. In addition, the application prospects and current trends of research and development of quantum dot phosphors are also discussed.

• Architectural research
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• v.7 no.2
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• pp.81-89
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• 2005

Over the years, existing bridges have had various degrees of maintenance to extend the service life. As the existing bridges continue to deteriorate, however, each Department of Transportation (DOT) of the United States of America faces increasing demands on the limited funds available for bridge maintenance. Therefore, it is very important for State Department of Transportations to establish Maintenance, Repair, and Rehabilitation (MR&R) strategies for bridge structures such that funds get allocated for appropriate maintenance over the service life. This paper identifies the state-of-art and the state-of-practice of MR&R actions and the use of MR&R strategies in concrete bridge decks. In addition, a questionnaire survey was conducted to identify the type and timing for MR&R actions as well as existing MR&R strategies taken in concrete bridge deck by each DOT. This paper also presents the results of the survey.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.808-813
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• 2005

Effective cost management requires reliable cost estimates at every stage of project development. The primary purpose of this research is to develop systematic modeling procedures and an automatic computing program for infrastructure estimating in the Texas Department of Transportation (TxDOT). The computing system toggles between project input information and segregated district unit prices for highway work item quantity estimates associated with earthwork and landscape, subgrade treatments and base, surface courses and pavement, structures, miscellaneous construction, and lighting, signing, markings and signals. This quantity-based approach was chosen because of the conventional approach lacking of quantity information until primary design is complete.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1579-1582
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• 2005

철도 운전사고의 대부분을 차지하는 철도건널목에 대한 기존의 사고예측식은 국외의 경우 Peabody Dimmick Formula, New Hampshire Index, National Cooperative Highway Research Program(NCHRP) report 50, U.S. Department of Transportation(DOT) 사고예측식 등을 이용하고 있었으며, 국내의 경우, U.S. DOT 사고예측식의 입력변수를 다변량 분석법을 이용하여 국내에 맞게 조정한 사고예측식을 이용하고 있다. 그러나 위에서 제시한 철도건널목 사고예측식은 철도건널목에서 발생하는 사고를 단순히 철도통행량, 도로통행량, 선로수, 도로수 등의 요인에 국한하여 분석한 것이고, 사고예측식 자체가 철도건널목에만 국한된다는 맹점을 안고 있어서 철도건널목장치라든지 철도건널목을 이용하는 사람들의 성향 등, 여러 인자를 고려한 철도건널목에서의 안전성분석 및 대책을 제시할 필요가 있다. 본 논문에서는 철도건널목장치를 포함하여 다른 시스템에도 범용적으로 적용할 수 있고, 제한된 변수에만 국한하지 않아 여러 사항을 고려할 수 있는 안전성분석 절차를 제시하였는데 이 안전성 분석 절차를 철도건널목에 적용함으로써 시스템의 위험요인을 분석하고, 이에 대한 원인 및 결과, 손실을 도출한 후 대책을 제시할 수 있었다.

• International Journal of Concrete Structures and Materials
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• v.8 no.3
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• pp.185-199
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• 2014

As the national transportation infrastructure ages and deteriorates, many existing bridges require frequent and costly maintenance and repairs. The objective of this work was to synthesize new and existing types of beam end coatings and treatments that have been proven to extend the life of new and existing concrete and steel bridge beams. A comprehensive literature review, along with online surveys and phone interviews of State department of transportations (DOTs) and coating manufacturers was conducted to gather information about existing and recently developed technologies. The study revealed that while many promising coatings and treatments are offered on the market, there is a lack of readily available laboratory results that would enable direct comparison of the available methods. This finding applies in terms of the coatings' durability and the potential for extending the service life of existing bridges. Most of the interviewed State DOTs' personnel assessed the products listed in respective DOT's Qualified Products Lists as performing 'well'. However, there was significant variability between states in the type of the products used. Among the agencies contacted, none was able to suggest the most promising or advanced products, either for concrete or steel bridge beam end treatments. This suggests that comprehensive laboratory evaluation would be necessary for selecting the best available beam end treatments and coatings.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.640-648
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• 2022

In the United States, the Safety Rest Areas (SRAs) were introduced as highway roadside infrastructures in the early 1900s. The State Departments of Transportation (DOTs) operate/maintain their SRAs using different methods. The Washington DOT used the in-house workforce method for over 20 years, whereas some states moved to Performance-Based Contracting (PBC) from the in-house workforce to save cost primarily. Several existing studies claimed that using the PBC approach saved costs on several highway assets. Thus, the principal objective of this study is to compute and compare the unit operating/maintenance cost of SRAs using the in-house workforce method (in Washington state) with the PBC approach (in other states). The findings of this study show that the average annual cost using the PBC approach was much more than the average annual cost using the in-house workforce approach. The findings also show that in Washington state, the 'Labor Cost' category was a key expenditure, which is statistically higher than other categories. The 'Labor Cost' was followed by the 'Other Services', and then 'Materials and Supplies' and 'Equipment.' The study's findings indicated that outsourcing does not always save costs for agencies. The study findings may help transportation construction/maintenance professionals select a cost-effective approach for their future planning.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.5
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• pp.233-240
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• 2012

White LEDs (light-emitting diodes) are promising new-generation light sources which can replace conventional lamps due to their high reliability, low energy consumption and eco-friendly effects. This paper briefly reviews recent progress of oxy/nitride host phosphor and quantum dot materials with broad excitation band characteristics for phosphor-converted white LEDs. Among oxy/nitride host materials, $M_2Si_5N_8$ : $Eu^{2+}$, $MAlSiN_3$ : $Eu^{2+}$ M-SiON (M = Ca, Sr, Ba), ${\alpha}/{\beta}$-SiAlON : $Eu^{2+}$ are excellent phosphors for white LED using blue-emitting chip. They have very broad excitation bands in the range of 440~460 nm and exhibit emission from green to red. In this paper, In this review we focus on recent developments in the crystal structure, luminescence and applications of the oxy/nitride phosphors for white LEDs. In addition, the application prospects and current trends of research and development of quantum dot phosphors are also discussed.

• Journal of Adhesion and Interface
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• v.19 no.4
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• pp.163-166
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• 2018

Dip-pen nanolithography(DPN) is an atomic force microscope (AFM) based method of generating nano- or micro-patterns. This technique has been used to transfer various ink materials on the substrate through water meniscus formed between AFM tip and the substrate surface. In this study, the heptadecafluoro-1,1,2,2-tetrahydrodecyltrimethoxysilane (HDFDTMS) ink materials were coated on the pre-coated AFM tip surface with the HDFDTMS molecules. When the tip brought into contact with the hydroxyl-functionalized silicon surface, HDFDTMS ink molecules have been successfully transported from the tip onto the surface via water meniscus. The created array and passivation area showed stable structures on the surface, and the transport of ink materials from the AFM tip to the surface followed linear increase in pattern size with contact time.