• 한국융합학회논문지
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• 제13권5호
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• pp.1-8
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• 2022

국내에서는 4차 산업혁명의 핵심기술인 드론 등을 이용하여 사회기반시설(SOC)를 디지털화하는 한국판뉴딜 정책을 추진 중에 있고, 국외에서도 열화상카메라 등 융복합센서를 드론에 탑재하여 다양한 산업 분야에서 활용하는 사례가 증가하고 있다. 본 연구에서는 고속도로 교면포장 공사에서 포장 품질을 개선하기 위하여 드론에 열화상 카메라를 탑재하여 포장 작업 구간에 대한 온도 측정 및 검증을 수행하였다. 기존의 방식인 레이저 온도계를 활용한다면 포장 온도를 부분적으로만 측정이 가능하지만, 제안된 방식을 활용하면 포장 작업 구간 전체에 대한 실시간 온도 모니터링 뿐 아니라 온도 분포 확인을 통한 균일성 검증이 가능한 것을 확인하였다. 제안된 방식을 현장에 적용한다면 도로 개방 시기(포장 표면온도≦40℃)에 대한 오판의 가능성을 낮춰줌에 따라 고속도로 포장 품질관리 제고 및 신속한 교통 개방 시기 결정이 가능할 것으로 기대된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.125-126
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• 2021

In order to improve the housing culture, construction changes for the utilization of diverse and multifunctional spaces are appearing in response to the increasing diverse needs of consumers. Cellular Light-weight Concrete (CLC) is being developed for use in fire-resistant heat-insulating walls and non-bearing walls. However, manufacturing non-uniformity has become a problem as a drawback due to the use of foamed bubbles and normal temperature curing, and additional research is required. Therefore, in order to suppress cracks due to drying shrinkage, silica sand is mixed with CLC to try to understand its characteristics. In the experiment, the compressive strength from 7 to 28 days of age was measured via a constant temperature and humidity chamber, and the drying shrinkage was analyzed according to each condition using a strain gauge. The compressive strength of matrix tends to decrease as the substitution rate of silica sand increases. This is judged by the result derived from the fact that the specific surface area of silica sand is smaller than that of slag. Based on KS F 2701 (ALC block), the compressive strength of 0.6 products is 4.9 MPa or more as a guide, so the maximum replacement rate of silica sand that satisfies this can be seen at 60%. Looking at the change in drying shrinkage for just 7 days, the shrinkage due to temperature change and drying is 0.7 mm, and the possibility of cracking due to shrinkage can be seen, and it seems that continuous improvement and supplementation are needed in the future.

• 대한토목학회논문집
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• 제26권5B호
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• pp.459-467
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• 2006

본 연구에서는 화력발전소 순환수취수로의 유량증가가 취수펌프장 흐름에 미치는 영향을 해석하고 개선하기 위하여 수리 및 수치모형실험을 수행하였다. 수치모형실험결과에 의하면 화력발전소 순환수취수로의 유량이 증가하면 취수로내의 유속과 순환수취수 펌프장의 연직방향와도가 증가하여 순환수취수 펌프장내의 와류발생가능성이 크게 증가하는 것을 알 수 있었다. 수리모형실험을 수행하여 순환수취수펌프장 유입부의 수면 근처 흐름은 거의 균등한 유량 배분이 이루어지고 반면에, 바닥 근처의 흐름은 유량 배분이 균등하게 이루어지지 못하여 취수펌프장내에서 역류현상이 발생하는 것을 밝혀냈다. 삼각형 도류벽을 취수펌프장 유입부에 설치하여 유속분포의 불균일성을 제거할 수 있었고 역류발생문제를 제거하였다.

• 한국재료학회지
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• 제33권11호
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• pp.491-496
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• 2023

As the demand for p-type semiconductors increases, much effort is being put into developing new p-type materials. This demand has led to the development of novel new p-type semiconductors that go beyond existing p-type semiconductors. Copper iodide (CuI) has recently received much attention due to its wide band gap, excellent optical and electrical properties, and low temperature synthesis. However, there are limits to its use as a semiconductor material for thin film transistor devices due to the uncontrolled generation of copper vacancies and excessive hole doping. In this work, p-type CuI semiconductors were fabricated using the chemical vapor deposition (CVD) process for thin-film transistor (TFT) applications. The vacuum process has advantages over conventional solution processes, including conformal coating, large area uniformity, easy thickness control and so on. CuI thin films were fabricated at various deposition temperatures from 150 to 250 ℃ The surface roughness root mean square (RMS) value, which is related to carrier transport, decreases with increasing deposition temperature. Hall effect measurements showed that all fabricated CuI films had p-type behavior and that the Hall mobility decreased with increasing deposition temperature. The CuI TFTs showed no clear on/off because of the high concentration of carriers. By adopting a Zn capping layer, carrier concentrations decreased, leading to clear on and off behavior. Finally, stability tests of the PBS and NBS showed a threshold voltage shift within ±1 V.

• The Journal of Advanced Prosthodontics
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• 제15권5호
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• pp.248-258
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• 2023

PURPOSE. This study aims to evaluate the effects of exposure energy on the lateral resolution and mechanical strength of dental zirconia manufactured using digital light processing (DLP). MATERIALS AND METHODS. A zirconia suspension and a custom top-down DLP printer were used for in-office manufacturing. The viscosity of the suspension and uniformity of the exposed light intensity were controlled. Based on the exposure energy dose delivered to each layer, the specimens were classified into three groups: low-energy (LE), medium-energy (ME), and high-energy (HE). For each energy group, a simplified molar cube was used to measure the widths of the outline (X_o and Y_o) and isthmus (X_i and Y_i), and a bar-shaped specimen of the sintered body was tested. A Kruskal-Wallis test for the lateral resolution and one-way analysis of variance for the mechanical strength were performed (α = .05). RESULTS. The zirconia green bodies of the ME group showed better lateral resolution than those of the LE and HE groups (both P < .001). Regarding the flexural strength of the sintered bodies, the ME group had the highest mean value, whereas the LE group had the lowest mean value (both P < .05). The ME group exhibited fewer agglomerates than the LE group, with no distinctive interlayer pores or surface defects. CONCLUSION. Based on these findings, the lateral resolution of the green body and flexural strength of the sintered body of dental zirconia could be affected by the exposure energy dose during DLP. The exposure energy should be optimized when fabricating DLP-based dental zirconia.

• 열처리공학회지
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• 제37권1호
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• pp.16-22
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• 2024

The conventional degreasing process involves removing oil and contaminants at temperatures above 80℃, resulting in excessive energy consumption, increased process costs, and environmental issues. In this study, we aimed to find the optimal degreasing conditions for the pre-treatment process of electro-galvanizing cold-rolled steel sheets, conducted efficiently at room temperature without the need for a separate heating device. To achieve this, we developed a room temperature degreasing solution and a brush-type degreasing tool, aiming to reduce energy consumption and normalize the decrease in degreasing efficiency caused by temperature reduction. Alkaline degreasing solution were prepared using KOH, SiO₂, NaOH, Na₂CO₃, and Sodium Lauryl Sulfate, with KOH and NaOH as the main components. To enhance the degreasing performance at room temperature, we manufactured additives including sodium oleate, sodium stearate, sodium palmitate, sodium lauryl sulfate, ammonium lauryl sulfate, silicone emulsion, and EDTA-Na. Room temperature additives were added to the alkaline degreasing solution in quantities ranging from 0.1 to 20 wt.%, and the uniformity of degreasing and the adhesion of the galvanized layer were evaluated through Dyne Test, T-bending Test, OM, SEM, and EDS analyses. The results indicated that the optimal degreasing solution composition consisted of NaOH (30 g/L), Na₂CO₃ (30 g/L), SLS (6 g/L), and room temperature additives (≤1 wt%).

• 한국전기전자재료학회논문지
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• 제37권5호
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• pp.554-561
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• 2024

Micro light-emitting diodes (µLEDs) have been utilized in various fields such as displays, and smart devices, due to their superior stabilities. Since the applications of the µLEDs have been extended to medical devices and wearable sensors, excellent optical properties and uniformity of the µLEDs are important. Hence, several researchers have investigated to enhance the optical efficiency of the µLEDs through micro/nano lens. However, the reported methods for realizing the micro/nano lens have some drawbacks such as complex and high-cost manufacturing processes. Herein, we developed µLEDs with 3D-printed hydrogel microlenses. The printed hydrogel had high transparency and excellent adhesive strength, allowing it to attach onto top surface of the µLEDs without any additional adhesives. Microscale printing technology using a 3D printer achieved quick and fine printing in desired shapes and arrangements, showing the possibility of mass production. The 3D-printed microlens can be applied to improve not only the optical properties of µLEDs but also other optical devices.

• 한국산림과학회지
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• 제80권2호
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• pp.151-161
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• 1991

화분(花粉)의 특징(特徵)으로서 우리나라에서 자라고 있는 참나무과(科)의 분류군(分類群)을 식별(識別)하고자 하였다. 5속(屬) 19종류(種類)의 화분(花粉)에 대(對)하여 광학현미경(光學顯微鏡)과 주사형전자현미경(走査型電子顯微鏡) 관찰(觀察)로서 얻은 결과(結果)는 다음과 같다. 1. 본과(本科)의 화분(花粉)은 4개(個)의 주형(主型)과 4개(個)의 부형(副型)(Quercus)으로 분류(分類)되었다. 1) 너도 밤나무형(型) 2) 밤나무형(型) 3) 돌참나무, 잣밤나무형(型) 4) 참나무형(型) (1) 가시나무부형(副型) (2) 갈참나무부형(副型) (3) 떡갈나무부형(副型) (4) 상수리나무부형(副型) 2. 화분(花粉)의 과립상문(顆粒狀紋)의 형태(形態)는 참나무속(屬)의 각두인편(殼斗鱗片)의 형태분화(形態分化)와 관계(關係)가 깊은 것으로 나타났다. 1) 화분표면(花粉表面)의 균일(均一)한 분기과립상문(分岐顆粒狀紋)은 각두인편(殼斗鱗片)이 동심원상(同心圓狀)으로 배열(配列)하는 형질(形質)과 상응(相應)되었다. 2) 화분표면(花粉表面)에 대소과립(大小顆粒), 단과립(單顆粒)과 괴상과립(塊狀顆粒)등이 혼재(混在)하고 괴상과립상(塊狀顆粒狀)의 소철점(小凸占)이 구형(球型)인 형질(形質)은 단인편상각두(短鱗片狀殼斗) 형질(形質)에 상응(相應)하였다. 3) 화분표면(花粉表面)에 대소과립(大小顆粒), 단과립(單顆粒)과 괴상과립(塊狀顆粒)등이 혼재(混在)하고 괴상과립(塊狀顆粒)의 선단(先端)이 Amoeba형(型)을 이루는 형질(形質)은 떡갈나무와 같이 각두인편(殼斗鱗片)이 박질세장(薄質細長)한 형질(形質)과 상응(相應)하였다. 4) 화분표면(花粉表面)에 대소과립(大小顆粒)이 혼재(混在)하나 단과립문(單顆粒紋)만 있는 형질(形質)은 상수리나무의 각두(殼斗)와 같이 후질세장(厚質細長)한 각두인편(殼斗鱗片)의 형질(形質)과 상응(相應)하였다. 3. 화분표면(花粉表面)의 무늬형태(形態), 표면미공(表面微孔)의 유무(有無), 화분잎(花粉粒)의 크기 및 과립(顆粒)의 형태(形態)를 수량화(數量化)하여 Cluster분석(分析)을 한 결과(結果)는 기(旣) 식물계통(植物系統) 분류체계(分類體系)와 잘 부합(符合)되었고 종이하수준(種以下水準)에서도 유연관계(有緣關係)를 잘 나타내 주었다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2005년도 ISMP
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• pp.201-212
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• 2005

[ $Epoxy/BaTiO_3$ ] composite embedded capacitor films (ECFs) were newly designed fur high dielectric constant and low tolerance (less than ${\pm}15\%$) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of specially formulated epoxy resin and latent curing agent, and in terms of coating process, a comma roll coating method is used for uniform film thickness in large area. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ composite ECF is measured with MIM capacitor at 100 kHz using LCR meter. Dielectric constant of $BaTiO_3$ ECF is bigger than that of $SrTiO_3$ ECF, and it is due to difference of permittivity of $BaTiO_3\;and\;SrTiO_3$ particles. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ ECF in high frequency range $(0.5\~10GHz)$ is measured using cavity resonance method. In order to estimate dielectric constant, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing the frequencies of the resonant cavity modes. About both powders, calculated dielectric constants in this frequency range are about 3/4 of the dielectric constants at 1 MHz. This difference is due to the decrease of the dielectric constant of epoxy matrix. For $BaTiO_3$ ECF, there is the dielectric relaxation at $5\~9GHz$. It is due to changing of polarization mode of $BaTiO_3$ powder. In the case of $SrTiO_3$ ECF, there is no relaxation up to 10GHz. Alternative material for embedded capacitor fabrication is $epoxy/BaTiO_3$ composite embedded capacitor paste (ECP). It uses similar materials formulation like ECF and a screen printing method for film coating. The screen printing method has the advantage of forming capacitor partially in desired part. But the screen printing makes surface irregularity during mask peel-off, Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. Using $epoxy/BaTiO_3$ composite ECP, dielectric constant of 63 and specific capacitance of 5.1nF/cm2 were achieved.

• 한국토양비료학회지
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• 제49권2호
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• pp.208-217
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• 2016

The Rural Development Administration moved to Jeonju for the balanced development of the land. This situation required establishment of new research fields with soils appropriate to cultivation. We applied a variety of amelioration techniques to mature soils of new research fields of the National Institute of Agricultural Science (NAS) and evaluated effects of the integrated amelioration techniques. The schedule of amelioration was following: 1) location of research fields was determined, 2) surface and subsoil samples were collected separately, 3) after aligning the top level of research fields, subsoil and surface soil were re-established with soil amendment, 4) the green manure crops were grown four seasons to improve the uniformity and increase the organic content of the research field, and 5) drainage canal and/or underdrainage were applied to poorly drained fields. The last green manure crop was rape in RDA fields and green barley in NAS fields. The average height, fresh weight, and dry matter weight of rape in good condition were 123 cm, $3,938kg\;10a^{-1}$, and $651kg\;10a^{-1}$, respectively. The height, fresh weight, and dry matter of green barley, on average, were 97 cm, $3,013kg\;10a^{-1}$, and $1,004kg\;10a^{-1}$, respectively. In the chemical properties of paddy field, pH and levels of silicate, calcium, magnesium, and potassium were in appropriate range but organic matter content of $16g\;kg^{-1}$ was less than the optimum level. In the chemical properties of upland field, pH and levels of phosphorus, calcium, magnesium, and potassium were appropriate range but organic matter content of $12g\;kg^{-1}$ was less than the optimum range. Evaluation of well-adapted soil was performed. The field in RDA was classified into the superior class with points ranging from 90 to 95 by the field evaluation test. The fields in NAS were mainly evaluated as the superior class with points greater than 85. However, some fields in NAS remained low quality with scores between 80 and 83. Further soil amelioration practices were suggested to fields with low soil quality.