• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.4
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• pp.37-49
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• 2015

The goal of this research is to examine air temperature changes according to tree type, plantation type, roadside green area structure, and green volume of street green area within a city. The plantation type that could be analyzed for comparison by tree type with over 3 species was 1 rows of tree+shrubs. The results of analysis of average air temperature difference between pedestrian and car streets vis-a-vis 1 row of tree+shrub in high air temperature areas were: Pinus densiflora, $1.35^{\circ}C$; Zelkova serrata, $1.84^{\circ}C$; Ginkgo biloba, $2.00^{\circ}C$; Platanus occidentalis, $2.57^{\circ}C$. This standard large wide canopy species was analyzed by the roadside to provide shade to have a significant impact on air temperature reduction. In terms of analysis of the relationship between plantation type of roadside trees and air temperature, the average air temperature difference for 1 row of tree type was $1.80^{\circ}C$; for 2 rows of trees it was $2.15^{\circ}C$. In terms of analysis of the relationship between the roadside green area structure and air temperature, for tree type, average air temperature $1.94^{\circ}C$: for tree+shrub type, average air temperature $2.49^{\circ}C$; for tree+mid-size tree+shrub type, average air temperature $2.57^{\circ}C$. That is, air temperature reduction was more effective in a multi-layer structure than a single layer structure. In the relationship analysis of green volume and air temperature reduction, the air temperature reduction effect was enlarged as there was a large amount of green volume. There was a relationship with the green volume of the road, the size of the tree and number of tree layers and a multi-layer structured form of planting. The canopy volume was large and there were a great number of rows of the tree layer and the plantation type of multi-layer structure, which is what is meant through a relationship with the green volume along the roadside. Green composition standards for air temperature reduction effects and functional improvement were proposed based on the result. For a pedestrian street width of 3m or less in the field being ideal, deciduous broadleaf trees in which the canopy volume is small and the structure of the tree+shrub type through the greatest 1m green bend were proposed. For a pedestrian street width of over 3m, deciduous broadleaf trees in which the canopy volume is large and is multi-layer planted with green bend over 1m, tree+mid-size tree+shrub type was proposed.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.531-540
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• 2020

The whirl and generated forces of rotating cylinders with different diameters placed in still water and in flow are studied experimentally. For the rotating cylinders in still water, the Same Frequency Whirl (SFW) and Different Frequency Whirl (DFW) have been identified and illustrated. The corresponding SFW and DFW areas are divided. The Root Mean Square (RMS) values of the generated force coefficient dramatically increase in the defined ranges of Resonance I and Resonance II. For the rotating cylinders in flow, the hydrodynamics, SFW and DFW are illustrated. The hydrodynamic, SFW and DFW areas are divided. The RMS values of the generated forces in the range of Resonance II are much smaller than those in still water due to the generated lift forces. The discussion suggests that the frequency of the DFW may equal multiple times or one-multiple times that of the rotating frequency: the whirl direction of the DFW with multiple times the frequency of the rotating frequency is the same as the rotating direction. The whirl direction of the DFW with one-multiple times frequency of the rotating frequency is opposite to the rotating direction.

• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.63-68
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• 2015

A one-step fabrication of a photonic crystal (PC) with functional defects is demonstrated. Using multi-beam phase-controlled holographic lithography with a diffracting optical element, large area one dimensional (1D) and two dimensional (2D) PCs with periodic defects were fabricated. The uniform area is up to $2mm^2$, and tens of defect channels have been introduced in the 1D and 2D PC structure. This technique gives rise to substantial reduction in the fabrication complexity and significant improvement in the spatial accuracy of introducing functional defects in photonic crystals. This method can also be used to design and fabricate three dimensional (3D) PCs with periodic defects.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.3-23
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• 2017

The achievement of tissue engineering can be highly depending on the capability to generate complicated, cell seeded three dimensional (3D) micro/nano-structures. So, various fabrication techniques that can be used to precisely design the architecture and topography of scaffolding materials will signify a key aspect of multi-functional tissue engineering. Previous methods for obtaining scaffolds based on top-down are often not satisfactory to produce complex micro/nano-structures due to the lack of control on scaffold architecture, porosity, and cellular interactions. However, a bioprinting method can be used to design sophisticated 3D tissue scaffolds that can be engineered to mimic the tissue architecture using computer aided approach. Also, in recent, the method has been modified and optimized to fabricate scaffolds using various natural biopolymers (collagen, alginate, and chitosan etc.). Variation of the topological structure and polymer concentration allowed tailoring the physical and biological properties of the scaffolds. In this presentation, the 3D bioprinting supplemented with a newly designed plasma treatment for attaining highly bioactive and functional scaffolds for tissue engineering applications will be introduced. Moreover, various in vivo and in vitro results will show that the fabricated scaffolds can carry out their structural and biological functionality.

• Journal of the Korean Society of Clothing and Textiles
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• v.41 no.2
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• pp.296-305
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• 2017

Gallnuts are known to exert various pharmaceutical properties that include anti-inflammatory, antimicrobial, antioxidant, and detoxifying effects. Gallnut extract is thought to be a particularly safe antimicrobial agent for textile application due to its natural origins. Hence, textiles were dyed with gallnut to develop multi-functional clothing material with no harmful effects. In this study, three kinds of cool touch woven fabrics, each comprised of 100% viscose rayon filament, viscose rayon filament/high absorption & quick dry (polyester) filament, and viscose rayon $filament/tencel^{(R)}$ spun yarn, were prepared and used as substrates for gallnut dyeing to especially develop functional cool touch textiles for summer clothing material. On the other hand, gallnut dyeing was conducted with mordanting with iron, lime or alum, which induced different colors on the dyed textiles. Dyed textiles were then investigated by SEM, FTIR, antibacterial test, and antioxidant test. Subsequently, gallnut dyed textiles indicated excellent antibacterial ability and deodorization activity regardless of mordant species. However, only gallnut dyed textiles mordanted with iron and alum showed significant antioxidant ability. In addition, the dyeing processes impair the cool touch feeling of the textiles by changing the micro structure of the textile surface.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6839-6845
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• 2015

The optimization design method for the broadband operation of the sleeve monopole was proposed to unify the multiple antennas essential to the multi-functional broadband wireless communication systems into one antenna. The structure of the sleeve part was optimized to enhance the impedance matching characteristics based on the theoretical analysis that sleeve part can works as the open stub. The thick monopole was used for the broadband operation. The radius of the sleeve and the permittivity of the dielectric inside the sleeve was optimized to enhance the impedance matching characteristics for the broadband operation. The optimized sleeve monopole having thick monopole shows broadband characteristics over 3:1 bandwidth, from 0.8 to 2.43 GHz, which is suitable for the commercial wireless communication system. The proposed broadband sleeve monopole can reduce multiple antennas essential to the multi-functional broadband systems to one antenna.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.491-491
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• 2011

Transparent and flexible electronic devices that are light-weight, unbreakable, low power consumption, optically transparent, and mechanical flexible possibly have great potential in new applications of digital gadgets. Potential applications include transparent displays, heads-up display, sensor, and artificial skin. Recent reports on transparent and flexible field-effect transistors (tf-FETs) have focused on improving mechanical properties, optical transmittance, and performances. Most of tf-FET devices were fabricated with transparent oxide semiconductors which mechanical flexibility is limited. And, there have been no reports of transparent and flexible all-organic tf-FETs fabricated with organic semiconductor channel, gate dielectric, gate electrode, source/drain electrode, and encapsulation for sensor applications. We present the first demonstration of transparent, flexible all-organic sensor based on multifunctional organic FETs with organic semiconductor channel, gate dielectric, and electrodes having a capability of sensing infrared (IR) radiation and mechanical strain. The key component of our device design is to integrate the poly(vinylidene fluoride-triflouroethylene) (P(VDF-TrFE) co-polymer directly into transparent and flexible OFETs as a multi-functional dielectric layer, which has both piezoelectric and pyroelectric properties. The P(VDF-TrFE) co-polumer gate dielectric has a high sensitivity to the wavelength regime over 800 nm. In particular, wavelength variations of P(VDF-TrFE) molecules coincide with wavelength range of IR radiation from human body (7000 nm ~14000 nm) so that the devices are highly sensitive with IR radiation of human body. Devices were examined by measuring IR light response at different powers. After that, we continued to measure IR response under various bending radius. AC (alternating current) gate biasing method was used to separate the response of direct pyroelectric gate dielectric and other electrical parameters such as mobility, capacitance, and contact resistance. Experiment results demonstrate that the tf-OTFT with high sensitivity to IR radiation can be applied for IR sensors.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.100-102
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• 2013

Magnetron-sputtering법을 사용하여 기존에 연구하였던 CrAlN (Cr 7：Al 3)박막에 Si를 첨가하여 Si의 함량 변화에 따라 미세구조와 화학적 결합상태, 온도저항계수(TCR) 및 산화저항의 영향과 기계적특성 개선을 통한 multi-functional heater resistor layer로써의 가능성을 연구하였다. CrAlSiN 박막의 Si 함량에 변화에 따라 온도저항계수 변화를 확인하였으며 X-선 회절 분석(XRD) 패턴 분석결과 CrAlSiN 박막의 결정구조가 Bl-NaCl 구조를 가지고 있는 것을 확인하였으며 SEM과 AFM을 통한 표면 및 미세구조 분석결과 Si의 함량이 증가할수록 입자가 조밀해짐을 알 수 있었다. 최근 digital priting technology의 핵심 기술로 부각되고 있는 inkjet priting technology는 널리 태양전지뿐만 아니라 thin film process, lithography와 같은 반도체 공정 기술에 활용 할 수 있기 때문에 반도체 제조장비에도 사용되고 있으며, 현재 thermal inkjet 방식을 사용하고 있다. Inkjet printing technology는 전기 에너지를 잉크를 배출하기 위해 열에너지로 변환하는 thermal inkjet 방식을 사용하고 있는데, 이러한 thermal inkjet 방식은 기본적으로 전기저항이 필요하지만 electrical resistor layer는 잉크를 높은 온도에서 순간적으로 가열하기 때문에 부식이나 산화 등의 문제가 발생할 수 있어 이에 대한 보호층을 필요로 한다. 하지만, 고해상도, 고속 잉크젯 프린터, 대형 인쇄 등을 요구되고 있어 저 전력 중심의 잉크젯 프린터의 열효율을 방해하는 보호층 제거에 필요성이 제기되고 있다. 본 연구는 magnetron-sputtering을 사용하여 기존의 CrAlN 박막에 Si를 합성하여 anti-oxidation, corrosion resistance 그리고 low temperature coefficient of resistance 값을 갖는 multi-functional heater resistor layer로써 CrAlSiN 박막의 Si 함량에 따른 효과에 초점을 두었다. 본 실험은 CrAlN 박막에 Si 함량을 4~11 at%까지 첨가시켜 함량의 변화에 따른 특성변화를 확인하였다. 함량이 증가할수록 amorphous silicon nitride phase의 영향으로 박막의 roughness는 감소하였으며 XRD 분석결과 (111) peak의 Intensity가 감소함을 확인하였으며 SEM 관찰시 모든 박막이 columnar structure를 나타내었으며 Si함량이 증가할수록 입자가 치밀해짐을 보여주었다.Si함량이 증가할수록 CrAlN 박막에 비하여 면저항은 증가하였으며 TCR 측정결과 Si함량이 6.5 at%일 때 가장 안정한 TCR값을 나타내었다. Multi-functional heater resistor layer 역할을 하기 위해서, CrAlSiN 박막의 원소 분포, 표면 거칠기, 미세조직, 전기적 특성 등을 조사하였다. CrAlN 박막의 Si의 첨가는 크게 XRD 분석결과 주상 성장을 억제 할 수 있으며 SEM 분석을 통하여 Si 함량이 증가할수록 Si3N4 형성이 감소하며 입자크기가 작아짐을 확인하였다. 면저항의 경우 Si 함량이 증가함에 따라 높은 면저항을 나타내었으며 Si함량이 6.5 at%일 때 가장 낮은 TCR 값인 3120.53 ppm/K값을 보였다. 이 값은 상용되고 있는 heater resistor보다 높지만, CrAlSiN 박막이 더 우수한 기계적 특성을 가지고 있기 때문에 hybrid heater resistor로 적용할 수 있을 것으로 기대된다.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.338-350
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• 2010

As existing materials for ground reinforcement, chemical grout material using cementitous materials and waterglass was used. But many problems in terms of ground reinforcement effects were implicated. In this study, for development and applicability verification of new materials, viscosity, fluidity, permeability, Self-Leveling, keeping of drilled hole, antiwashout underwater, resistance of water (groundwater dilution and minimize material eluting) and the early strength and long-term strength characteristics of developed materials was confirmed, and material standards, and establishing construction standards for the various model tests were conducted. As a result, high viscosity, flowability, permeability and keeping of drilled hole characteristics are excellent, in addition to the early strength properties, dilution does nat occur to groundwater, including groundwater is available for dealing with environmental issues. Application of basic and reinforcement method by Filler function in addition to structure can also or development of a new concept can be expected. In addition, middle and large-diameter drilled shaft, micropile, ground anchors, soil-nailing, steel pipes multi-grouting reinforcement for cement injection process could be used enough to even be considered.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.163-166
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• 2003

Laser-Induced Thermal Imaging (LITI) is a laser addressed patterning process and has unique advantages, such as high-resolution patterning with over-all position accuracy of the imaged stripes within 2.5 micrometer and scalability to large-size mother glass. This accuracy is accomplished using real-time error correction and a high -resolution stage control system that includes laser interferometers. Here the new concept of mixed hybrid system which complement the advantages of small molecular and polymeric materials for use as an OLED; our system can realize the easy processing of polymers and high luminance efficiency of recently developed small molecules. LITI process enables to pattern the stripes with excellent thickness uniformity and multi-stacking of various functional layers without using any type of fine metal shadow mask. In this study, we report a full-color hybrid OLED using the multi-layered structure of small molecular/polymeric species.