온실용 다겹보온자재의 보온성 비교 -Hot box 시험 결과를 중심으로-

윤성욱,이시영,강동현,손진관,박민정,김희태,최덕규 (사) 한국생물환경조절학회 2019 생물환경조절학회지 Vol.28 No.3

In this study, we conducted the hot box tests to compare the changes in thermal insulation for the four types of multi-layer thermal screens by the used period after collecting them from the greenhouses in the field when they were replaced at the end of their usage. The main materials for these four types of multi-layer thermal screens were matt georgette, non-woven fabrics, polyethylene (PE) foam, chemical cotton, etc. These materials were differently combined for each multi-layer thermal screen. We built specimens (70×70 cm) for each of these multi-layer thermal screens and measured the temperature descending rate, heat transmission coefficient, and thermal resistance for each specimen through the hot box tests. With regard to the material combinations of multi-layer thermal screens, thermal insulation can be increased by applying a multi-layered PE foam. However, it is considered that the multilayered PE foam significantly less contributes to heat-retaining than chemical wool that forms an air-insulating layer inside multi-layer thermal screens. For the suitable heat-retaining performance of multi-layer thermal screens, basically, materials with the function of forming an air-insulating layer such as chemical cotton should be contained in multi-layer thermal screens. The temperature descending rate, heat transmission coefficient, and thermal resistance of multi-layer thermal screens were appropriately measured through the hot box tests designed in this study. However, in this study, we took into consideration only the four kinds of multi-layer thermal screens due to difficulties in collecting used multi-layer thermal screens. This is the results obtained with relatively few examples and it is the limit of this study. In the future, more cases should be investigated and supplemented through related research. 본 연구에서는 현장 온실농가에서 수명이 다하여 교체작업이 이루어진 총 4종의 다겹보온자재를 채취하여 해당 사용기간별 보온성의 변화를 비교하기 위해 여기서고안된 Hot box 시험이 실시되었다. 4종의 다겹보온자재는 마트지, 부직포, PE폼 및 화학솜 등이 주요 재료로서 다겹보온자재별로 이 재료들이 서로 다르게 조합된형태였다. 이 4종의 다겹보온자재를 시편(70×70cm)으로제작하여 Hot box 시험을 통해서 대상시편별로 온도 하강률, 열관류율 및 열전도저항 등이 측정되었다. 그 결과를 요약하면 다음과 같다. 본 연구에서 사용된 다겹보온자재들에 대하여 적절한보온성능을 기대할 수 있는 사용기간은 약 5년 정도로예상되었다. 다겹보온자재의 재료조합에 대하여 다겹의PE폼을 적용하여 상대적으로 보온성을 높일 수 있으나다겹보온자재 내에서 공기 단열층을 형성하는 화학솜에비해 보온성능에 대한 기여가 현저히 낮은 것으로 판단되었다. 다겹보온자재에 대하여 적절한 보온성능을 기대하기 위해서는 기본적으로 화학솜과 같은 공기 단열층을형성하는 기능이 있는 재료가 다겹보온자재에 포함되어야 될 것으로 판단되었다. 본 연구에서 고안된 Hot box 시험을 통해 다겹보온자재의 온도 하강률, 열관류율 및 열전도저항 등이 적절하게 측정되었다. 그러나 본 연구는 사용이 완료된 다겹보온자재의 채취 어려움으로 총 4종의 다겹보온자재만고려되었으며, 이는 비교적 적은 사례로 통해 얻어진 결과라 할 수 있으며, 본 연구의 한계이다. 향후 관련 연구를 통해 더 많은 사례들이 조사 및 보완되어야 될 것이다.

다층 지르코니아 블록 종류와 설계위치에 따른 지르코니아 코핑의 기계적 특성 비교

강재민,김원영,정인성,전병욱 대한치과기공학회 2019 대한치과기공학회지 Vol.41 No.3

Purpose: This study was investigated the effect of multi-layer zirconia block type and design location on the mechanical properties of zirconia copings. Methods: Three kinds of multi-layered zirconia blocks (Snow princess multi layered block, Multi cherry, Dental zirconia pre-shaded blank) were used to identify the effects of the kinds of multi-layered zirconia blocks, design locations on mechanical characteristics of zirconia copings. 150 Zirconia copings were fabricated and fracture strength, hardness and microstructure were compared and evaluated. Results: Dental zirconia pre-shaded blank(2,256.9N) had the highest fracture strength of zirconia copings on all the design locations, and it was followed by Snow princess multi layered block(2,107.5N) and Multi cherry(917.0N). Snow princess multi layered block(1,949.7Hv) had the highest hardness of zirconia copings on all the design locations, and it was followed by Dental zirconia pre-shaded blank(1,671.7Hv) and Multi cherry(1,383.7Hv). The cervical layer had the highest fracture strength and hardness of zirconia copings in all the blocks, and it was followed by the cervical+gradation layer, the enamel layer, the enamel+gradation layer, and the gradation layer. Conclusion: It was found that the fracture strength and hardness were different according to the kinds of multilayer zirconia block and design location, and it was confirmed that it is lower than the fracture strength of white zirconia.

조경식재공간에서 다층식재의 실태분석 -수도권 아파트와 근린공원을 중심으로-

심우경,이동익 한국조경학회 2001 韓國造景學會誌 Vol.29 No.1

This study based on the theoretical understanding of multi-layer planting which have engineering, ecological and landscape benefits, was conducted to find out the status of multi-layer planting in the apartment and neighborhood park in Seoul. This study was also aimed to seek for the problematic matters, and suggest a solution on the current multi-layer planting. The results of this study were as follows; 1) Since landscape woody plants have been classified just as tree and shrub in Korea, the classification for the multi-layer planting has been unreasonable, and landscape woody plants might have been classified as tree, sub-tree and shrub, or upper, middle, and lower-layer, It could be defined that upper layer is over eight meters in full growth, middle over 3-8 meters and lower under 3 meters. 2) In apartments, the upper layer consisted of eighteen species, the middle and lower layer seven species each. In neighborhood parks, the upper layer consisted of fifteen species, and the middle and lower layer five species each. 3) In terms of planting year of the surveyed areas, there were no differences in the number of species when planting year of the apartment was divided into two groups, the first half(1900-1995) and the second(1996-2000). But, in terms of individual occupation, the percentage was decreased in upper layer, while there was increasing in middle and lower layer. 4) As the result of survey of multi-layered area, it appeared that apartment was shown 0.65 percent and neighborhood park 0.61 percent of the planted area, which was less than 1 percentage of landscape architecturally planted area. 5) In apartment, the number of individual in middle layers has been increased in the first half and the second, but with respect to the correlation with multi-layered area, the apartments had the "$\rho$=0.208", saying that increasing middle layer was scattered planting instead of multi-layered planting. 6) In planting at the apartments in Korea, the planting density was limited, because the layer division was restricted to only tree and shrub. On the contrary, it was divided into upper, middle and lower tree in Japan. Therefore, in Korea, it should be classified as the planting density by dividing into tree, sub-tree, and shrubs, or upper, middle and lower tree by the law. And, it should be considered that the multi-layered planting has a proper organic relation as well as the planting density.g density.

An interfacial layer to regulate self-folding of a multi-layered hydrogel

김상진,임준우,신성규,조성우,정재현 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

Multi-layered hydrogels has been studied for various applications including actuators and sensors. We designed multi-layered hydrogels with various expansion ratios. Each layer of multi-layered hydrogel was modulated at different mechanical properties that induced self-folding. Different mechanical properties of each layer controlled by the composition ratio adjust the radius of curvature of the multi-layered hydrogel. In this study, the presence of interfacial layers in multi-layered hydrogels was confirmed by fluorescence microscopy and gelation sequence control. Additionally, we discussed the interfacial layers of the multi-layered hydrogels.

New multi-layered zirconias: Composition, microstructure and translucency

Kolakarnprasert, Nantawan,Kaizer, Marina R.,Kim, Do Kyung,Zhang, Yu Elsevier 2019 Dental materials Vol.35 No.5

<P><B>Abstract</B></P> <P><B>Objectives</B></P> <P>To fully realize the range of indication and clinical advantages of the new multi-layered zirconias, a comprehensive understanding of their chemical composition, microstructure, low temperature degradation (LTD) resistance, and translucency properties is paramount.</P> <P><B>Methods</B></P> <P>A zirconia system (Katana, Kuraray Noritake), including 3 distinct grades of multi-layered zirconias, was selected for study: Ultra Translucent Multi-layered zirconia (UTML), Super Translucent Multi-layered zirconia (STML), and Multi-layered zirconia (ML). For different materials and their individual layers, the chemical composition, zirconia phase fractions, and microstructure were determined by X-ray fluorescence (XRF), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). Also, their resistance to LTD and translucency properties were characterized.</P> <P><B>Results</B></P> <P>Our findings revealed no major differences amongst layers, but the 3 materials were very distinct―UTML: 5Y-PSZ (5 mol% yttria-partially-stabilized zirconia) with ˜75 wt% cubic content and a 4.05 (±0.85) μm average grain size, STML: 4Y-PSZ with ˜65 wt% cubic content and a 2.81 (±0.17) μm average grain size, and ML: 3Y-PSZ with <50 wt% cubic content and a 0.63 (±0.03) μm average grain size. After water aging at 120 °C for 12 h, greater monoclinic content was found in ML. UTML and STML did not show detectable monoclinic phase. The translucency was similar among layers, and also between UTML and STML, which were superior to ML.</P> <P><B>Significance</B></P> <P>For each multi-layered zirconia grades, the layers are only differed in pigment types and contents, which yield remarkably natural shade gradients. Also, despite the significant compositional difference between STML and UTML, both materials showed similar translucencies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Composition differs amongst various grades of multi-layered zirconias, but similar among the layers within each material. </LI> <LI> UTML has the highest cubic content, followed by STML and ML. </LI> <LI> ML exhibits the lowest translucency, whereas UTML and STML show a similar level of translucency. </LI> <LI> Only pigment composition differs among the layers of each material, resulting in different shades but similar translucency. </LI> <LI> Only ML is susceptible to hydrothermal degradation. </LI> </UL> </P>

고려시대 당초문겹보관의 제작 배경과 특징

윤근영 미술사연구회 2018 미술사연구 Vol.- No.35

당초문겹보관은 보살상의 보관이면서도 동시대의 회화, 공예와도 연관된 고려시대의 중요한 종합예술품이다. 건칠상이나 목조상과 같이 규모가 큰 보살상의 경우 상과는 별도로 높이 15cm 내외의 금속제 보관을 제작해 씌우게 되는데, 그 중 동판을 여러 장 겹쳐 앞면을 만들고 전면을 당초문으로 장식한 것을 ‘당초문겹보관’이라 명명할 수 있다. 당초문겹보관을 착용한 고려시대의 보살상은 여말선초를 포함하여 13점 가량이며 13세기 초 안동 보광사 목조관음보살좌상의 보관이 가장 이른 시기의 것이다. 층단을 나누고 당초문을 세밀하게 새긴 高冠의 시원은 고려와 활발하게 교류하였던 중국 宋과 遼의 보살상에서 찾을 수 있다. 실제로 당초문겹보관이 전면에 당초문을 빽빽히 새긴 점이나 앞면 좌우에 꽃무늬를 대칭으로 새긴 점은 송대의 花冠과 유사하다. 또한 앞면을 여러 층으로 나눈 통형의 고관이라는 점은 요대 보살상과 상통하며, 1038년의 하화엄사 박가교장전 보살상에서는 앞을 여러 층으로 구획하고 금속끈으로 장식을 매단 보관을 볼 수 있다. 그러나 금속판을 여러 장 덧붙여 층을 낸 점과 감장 기법이 많이 사용된 점, 원권형 당초문을 투조로 새긴 금속제 보관이라는 점은 중국의 보관과는 구별되는 고려시대 당초문겹보관만의 독특한 특징이다. 이러한 당초문겹보관은 시대에 따라 그 구성이 크게 달라지지는 않으나 두 가지 유형으로 나누어 볼 수 있다. 첫째는 子板이 山形인 보관으로, 초기인 13세기와 14세기에 사례가 집중되어 있다. 둘째는 자판이 여의두형인 보관으로 산형 자판 보관보다는 후대에 출현한다. 산형 자판 보관은 다양한 문양과 조금 기법을 이용해 표면을 장식하는 데 집중하였는데 고려 중기에 유행했던 고육각 타출 기법이 두드러지게 나타난다. 이에 반해 여의두형 자판 보관은 바탕의 꾸밈은 상대적으로 단순하지만, 봉황․구름․화염보주 등의 큰 장식을 붙이고 감장 기법을 적극적으로 활용한 특징을 보인다. 당초문겹보관이 제작된 고려시대는 금속공예 기술의 전성기로서 왕실이나 고위층으로부터 많은 경제적 후원을 받아 수공업이 발달했던 시기였다. 또한 당초문겹보관이 등장하는 13세기는 무신집권기와 대몽항쟁기에 해당하는데, 이 시기에는 중국과의 교류가 축소되면서 중국과는 구별되는 독자적인 기법과 문양을 사용한 작품이 많이 등장하였다. 당초문겹보관이 중국의 보관 양식으로부터 영향을 받았으나 당시 자국의 회화나 공예에서 찾아볼 수 있는 문양을 새기고 전통적 기법을 써서 보석을 감장한 것은 이 시기 고려 공예품의 독자적 면모를 반영한 것이다. 고려시대 당초문겹보관의 또다른 의의는 이 보관이 조선시대의 보관 양식에 큰 영향을 주었다는 점이다. 조선 15세기의 당초문겹보관은 고려후기 당초문겹보관의 전통을 충실히 따르고 있으나 16세기 이후가 되면 상류층의 불사가 어려워지게 되며 당초문겹보관의 제작 역시 줄어들게 된다. 이를 대신해 목제 보관이 조선시대 보관의 주류가 되는데, 이 경우에도 표면의 당초문 표현이나 두 단으로 나누어진 앞면, 앞뒤의 접합부분이 표현된 것이 확인된다. 이를 종합하면 고려시대의 당초문겹보관은 당시 금속공예 기법의 정수를 보여 주는 독창적인 예술품인 동시에 그 형태와 문양에 있어 이후의 보관 양식에 큰 영향을 미쳤음을 알 수 있다. Multi-layered scroll-patterned crowns were used as crowns for bodhisattva statues, but are also important Goryeo artworks in general terms thanks to their links to the period's painting and crafts. Metal crowns approximately 15 centimeters in height were produced separately and placed on the heads of large bodhisattva statues made of materials such as dry lacquer or wood. Among these, those with fronts made of several bronze sheets and featuring foliage scroll patterns on all sides are sometimes known as “multi-layered scroll-patterned crowns.” Some 13 bodhisattva statues from the Goryeo period, including the period of transition to the subsequent Joseon dynasty, wear multi-layered scroll-patterned crowns; the earliest of these is a wooden statue of a seated Avalokitesvara bodhisattva that dates from the early 13th century and is now located at Bogwangsa Temple in Andong. The origins of tall crowns with intricately engraved foliage scroll patterns on multiple tiers lie in China's Song and Liao dynasties, both of which interacted extensively with Goryeo. Indeed, the densely engraved scroll patterns on the front of Goryeo multi-layered scroll-patterned crowns, and the flower patterns to the left and right of them, show similarities to the flower crowns (花冠) of Song. And the cylindrical shape, divided into multiple tiers, is a feature shared with Liao bodhisattva statues; the Sutra Hall of the lower monastery at Huayan Temple in Datong, Shanxi Province, China, built in 1038, houses a bodhisattva statue with a crown of which the front part is divided into several layers and adorned with decorations hanging on gold thread. But adding several metal plates to create layers, extensive use of stone setting techniques and carved openwork circle-shaped scroll patterns in metal crowns are unique features of Goryeo-era multi-layered scroll-patterned crowns that distinguish them from Chinese crowns. Though these crowns show no great differences according to period, they can be divided into two types. The first type of crown features a small plate shaped like a mountain; these crowns were produced primarily in the 13th and 14th centuries. The second type of crown features a small plate in the shape of a cloud; this type appears later than the first. The makers of crowns with mountain-shaped plates focused on surface decoration using diverse patterns and metal craft techniques; these crowns are striking for their use of highly pronounced repoussé and chasing, a technique fashionable in the mid-Goryeo period. Crowns with cloud-shaped plates, by contrast, are characterized by relatively simple decoration on their bases but also by the addition of large decorative elements such as phoenixes, clouds and auspicious figures and active use of stone setting techniques. The Goryeo period, during which multi-layered scroll-patterned crowns were produced, was a golden age for metalwork. Artisans received much financial support from the royal court and the nobility, helping develop handcrafts. The 13th century, when these crowns first appeared, was a time when military officials took power in Goryeo and the country struggled to resist the Mongols. At the same time, exchange with China was reduced, leading to the emergence of many craft items featuring unique techniques and patterns, distinct from those of China. Multi-layered scroll-patterned crowns ere influenced by Chinese crown styles, but their engravings of patterns found in Goryeo paintings and crafts, and their use of a traditional Goryeo technique for setting gemstones, reflect a unique aspect of Goryeo crafts at the time. Another significant aspect of Goryeo multi-layered scroll-patterned crowns is the strong influence they had on the crowns of the subsequent Joseon period. 15th century Joseon multi-layered scroll-patterned crowns faithfully followed the traditions of their late-Goryeo counterparts. But from the 16th century onwards it became more difficult for the upper class...

Effect of diffusion layer on self-folding of a multi-layered hydrogel

김상진,임준우,신성규,조성우,정재현 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Multi-layered hydrogels has been studied for various applications including actuators and sensors. We designed a multi-layered hydrogel with a different expansion ratio. Each layer of multi-layered hydrogel was composed of acrylamide (AAm) and N,N’-methylenebisacrylamide (MBA) at different concentrations and induced self-folding due to the difference in the expansion ratio of each layer. The radius of curvature of the multi-layered hydrogel was adjusted by the elastic modulus and expansion ratio of each layer. The physical properties of each layer were controlled by the composition ratio. In this study, the difference with the curvature of the produced hydrogel and the curvature calculated by conventional equation is discussed. Additionally, we present the diffusion layer generated in the produced multi-layered hydrogel and analyze the effect of diffuse layer.

Tuning the self-folding of a multi-layered hydrogel with interfacial zone

김상진,임준우,신성규,조성우,홍석현,최지현,정재현 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

Multi-layered hydrogels has been studied for various applications including actuators and sensors. We designed multi-layered hydrogels with various expansion ratios. Each layer of multi-layered hydrogel was modulated at different mechanical properties that induced self-folding. Different mechanical properties of each layer controlled by the composition ratio adjust the radius of curvature of the multi-layered hydrogel. In this study, the presence of diffusion layers in multi-layered hydrogels is confirmed by fluorescence microscopy and magnetic resonance imaging (MRI). Additionally, we discussed the diffusion layers of the multilayer hydrogels.

Failure and Phase Transformation Mechanism of Multi-Layered Nitride Coating for Liquid Metal Injection Casting Mold

Jeon, Changwoo,Lee, Juho,Park, Eun Soo Materials Research Society of Korea 2021 한국재료학회지 Vol.31 No.6

Ti-Al-Si target and Cr-Si target are sputtered alternately to develop a multi-layered nitride coating on a steel mold to improve die-casting lifetime. Prior to the multi-layer deposition, a CrN layer is developed as a buffer layer on the mold to suppress the diffusion of reactive elements and enhance the cohesive strength of the multi-layer deposition. Approximately 50 nm CrSiN and TiAlSiN layers are deposited layer by layer, and form about three ㎛-thickness of multi-layered coating. From the observation of the uncoated and coated steel molds after the acceleration experiment of liquid metal injection casting, the uncoated mold is severely eroded by the adhesion of molten metallic glass. On the other hand, the multi-layer coating on the mold prevents element diffusion from the metallic glass and mold erosion during the experiment. The multi-layer structure of the coating transforms the nano-composite structured coating during the acceleration test. Since the nano-composite structure disrupts element diffusion to molten metallic glass, despite microstructure changes, the coating is not eroded by the 1,050 ℃ molten metallic glass.

Wheelchair Multi-layer headrest foam 특성과 상해지수간 상관관계 분석

조성욱 ( Sungwook Cho ),지승민 ( Seungmin Ji ),전성식 ( Seong S. Cheon ) 한국복합재료학회 2023 Composites research Vol.36 No.4

Although the development of transportation means has realized the right to mobility for the disabled who have difficulty in moving, it can be said that the improvement of the safety of passengers with disabilities that can occur in a car accident is lower than that of ordinary passenger seats. In particular, in the case of a rear-end collision that can occur suddenly, it is a reality that disabled passengers are vulnerable to head and neck injuries. Therefore, in this study, a multi-layer headrest foam that divides the headrest into three parts in the coronal plane was proposed to improve the head and neck injury index of disabled passengers in the vehicle in the event of a rear-end collision of a wheelchair transport vehicle. A range of stress scale factors was selected to give various compressive characteristics of the foam through low-speed rear-end collision analysis through a simple model, and GA optimization was performed by specifying the range as a parameter. Through the optimization result, the phase relationship between HIC and NIC was analyzed according to the compression characteristics of the layers. HIC responded most sensitively to the compression characteristics of the front layer and NIC responded to the compression characteristics of the mid layer, and the compression characteristics of the rear layer showed the lowest. A normal headrest and an optimized multi-layer headrest were placed in the validation model to analyze the lowspeed rear-end collision sled test, and HIC and NIC were derived lower in the multi-layer headrest than in the general headrest. The compression behavior of the multi-layer headrest was also clearly shown, and it was verified that the multi-layer headrest was effective in improving the injury index of the head and neck compared to the general headrest.