• 한국표면공학회지
• /
• 제47권6호
• /
• pp.347-353
• /
• 2014

We present a synthesis of single-walled carbon nanotubes(SWNTs) for enhancement of parallel-alignment and density using chemical vapor deposition with methane feed gas. As-purchased ST-cut quartz substrates were heat-treated and line-patterned by electron-beam lithography in order to grow SWNTs with parallel alignment. We investigated the effects of various synthesis parameters such as catalyst oxidation, reduction, and synthesis conditions in order to enhance both tube density and degree of parallel alignment. The condition of $1{\AA}$ of Fe catalyst film, atmospheric oxidation at $750^{\circ}C$ for 10 min, reduction under 400 Torr for 5 min, and growth at $865^{\circ}C$ under 300 Torr yields $33tubes/10{\mu}m$, which is the highest tube density with parallel alignment. Based on the results of atomic force microscope and Raman spectroscopy, it was found that SWNTs have diameter range of 0.8-2.0 nm. We believe that the present work would contribute to the development of SWNTs-based flexible functional devices.

• Structural Engineering and Mechanics
• /
• 제73권5호
• /
• pp.501-513
• /
• 2020

In the present work, the optimization of machining parameters to achieve the desired technological parameters such as surface roughness, tool radial vibration and material removal rate have been carried out using response surface methodology (RSM). The hard turning of EN19 alloy steel with coated carbide (GC3015) cutting tools was studied. The main problem faced in manufacturer of hard and high precision components is the selection of optimum combination of cutting parameters for achieving required quality of surface finish with maximum production rate. This problem can be solved by development of mathematical model and execution of experiments by RSM. A face centred central composite design (FCCD), which comes under the RSM approach, with cutting parameters (cutting speed, feed rate and depth of cut) was used for statistical analysis. A second-order regression model were developed to correlate the cutting parameters with surface roughness, tool vibration and material removal rate. Consequently, numerical and graphical optimization were performed to obtain the most appropriate cutting parameters to produce the lowest surface roughness with minimal tool vibration and maximum material removal rate using desirability function approach. Finally, confirmation experiments were performed to verify the pertinence of the developed mathematical models.

• 한국태양에너지학회 논문집
• /
• 제28권5호
• /
• pp.28-35
• /
• 2008

The aim of this study was to analysis the Heating/cooling performance of movable insulation system built in apartments. The process of this study is as follows: 1) Test-cells of movable insulation are designed through the investigation of previous paper and work. The type of the movable insulation used in test-cell is low emissivity(5%) insulation, measured for heating season and the thermal effects are analyzed. 2) The simulation program(Design Builder) was used in energy performance analysis. the reference model of simulation was made up to analysis energy performance on movable insulation system. 3) Selected reference model(Floors:15, Area of Unit:115.5$m^2$) for heating/cooling energy analysis, Energy performance simulation with various variants, such as slate angle of movable insulation(5$^{\circ}$, 30$^{\circ}$, 50$^{\circ}$) and position of movable insulation. Consequently, When movable insulation system is equipped with balcony window of Apartment, Annual heating energy of reference model was cut down at the average of 5.4kWh/$m^2$ or 4.6% of heating/cooling energy.

• Safety and Health at Work
• /
• 제10권3호
• /
• pp.327-335
• /
• 2019

Background: There have been some concerns related to manual handling of large items in industry. Manual handling operations of large sheet metal may expose workers to risks related to efficiency as well as occupational safety and health. Large sheet metals are difficult to move and burdensome to lift/transfer, and handling the sharp sheet edges may result in contact stress and/or cut injuries on the workers. Methods: Through observation, interview, and immersive simulation activities, a few problems related to current handling of sheet metals were identified. A sheet metal trolley-lifter was then designed and fabricated to address these issues. A pilot study on the use of the developed trolley-lifter for handling sheet metals was conducted to compare between the new and traditional handling methods. Results: The pilot study of the trolley-lifter showed promising results in terms of improving the cycle time, manpower utilization, and working postures compared with the traditional handling method. Conclusion: The trolley-lifter offers an alternative solution to automation and a mechanized assistive device by providing a simple mechanism to assist the handling of sheet metals effectively and safely.

• Journal of information and communication convergence engineering
• /
• 제16권4호
• /
• pp.252-257
• /
• 2018

A wideband double radiator circular disc annular monopole antenna is proposed is this work. The radiators are etched on the surfaces of two Taconic TLY-5 substrates with a circular hole cut out of each of the radiators initially at the centers of the radiators with subsequent downward displacement of the holes. The antenna is designed with a two-step feeding transformer system for impedance matching between the input power source supplied by a $50-{\Omega}$ SMA connector and the monopole radiators. The transformer system improves the bandwidth performance at higher frequencies. The proposed antenna achieves a wideband having the capability of working between 0.645 and 18.775 GHz, corresponding to a -10 dB bandwidth of 186.7% with gain ranging from 0.95 to 8.26 dBi. In comparison to other metal disc planar monopole antennas, the proposed antenna has a small total size width due to the size of the ground plane, which has a diameter 100 mm. The frequency range of the antenna provides applications in global positioning systems, mobile communications, ultra-wideband short distance communications, and wireless computer networks.

• 멤브레인
• /
• 제31권4호
• /
• pp.282-292
• /
• 2021

본 연구에서는 Dead-end와 Crossflow 시스템을 사용하여 유기용매 나노여과(Organic Solvent Nanofiltration, OSN) 상용분리막의 성능을 분석하였다. 가교된 polyimide 소재 기반의 Duramem (DM) OSN 분리막의 성능을 ethanol, dimethylformamide (DMF), acetone, acetonitrile 용매에서의 성능을 분석하였다. 네 종류의 분획분자량 성능을 갖는 DM 분리막의 성능을 평가하였을 때 dead-end보다 Crossflow에서 조금 더 정확하고 신뢰성 높은 결과를 얻을 수 있었으며, 동일한 분리막이더라도 용매의 특성에 따라 투과도와 선택도 차이가 크게 난다는 것을 확인할 수 있었다. 이는 압밀화현상으로 인한 초기 안정화 기간의 차이 때문인 것으로 판단되며 분리막마다 안정화기간이 다르므로 신뢰성 높은 결과를 얻기 위해선 Crossflow 시스템을 활용하는 것이 더 적합한 것으로 보인다.

• 농업과학연구
• /
• 제47권4호
• /
• pp.727-742
• /
• 2020

Point cloud-based 3D maps can obtain many kinds of information for maintenance work on forest road networks. This study was conducted to compare the importance of each factor to select the factors required for the mapping of 3D forest road maps. This can be used as basic data for attribute information required to maintain forest road networks. The results of this study found that out of a total of 30 indexes extracted for mapping 3D forest roads, a total of 21 indexes related to stakeholder groups were significantly different. The importance of the index required by the civil service group was significantly higher than that of the other groups overall. In the case of the academic group, the index importance for cut slope, fill slope, and drainage facility was significantly higher. On the other hand, the index importance for the forestry cooperative and forest professional engineer group was mostly distributed between the civil servants' group and the academic group. In particular, the type of drainage system showed the highest value among the detailed indexes. Overall, drainage related factors in this survey had high coefficient values. The impact of water on forest roads was the most important part in road maintenance. In addition, the soil texture had a high value in relation to slope stability. This is thought to be because the texture of the soil affects the stability of the slope.

• 대한건축학회논문집:구조계
• /
• 제34권3호
• /
• pp.69-76
• /
• 2018

General workers who assist various technicians in different fields with their work across the whole construction sites without having a particular skill are at risk of the highest accident rate and their accident form becomes varied. Accordingly, this study was conducted to identify the relationship between form of safety accident and influence factor in general workers and analyze accident severity by influence factor. The followings are the results from this study. First, as a result of analyzing major form of accident and influence factors in general workers with network analysis methodology, nine forms of accident and seventeen influence factors were drawn. Second, it was found that in accident severity among general workers, collapsing, among various forms of accident, appeared the highest, followed by fall, electric shock, fire, hit by an object, bumped against, trip, scission getting cut chopped in order. Third, main points of special, concentrated, and permanent management were presented in order to reduce the safety accident in general workers effectively.

• Advances in concrete construction
• /
• 제11권2호
• /
• pp.173-181
• /
• 2021

The main objective of this work is to contribute to the valorization of plastic and glass waste in the improvement of concrete properties. Waste glass after grinding was used as a partial replacement of the cement with a percentage of 15%. The plastic waste was cut and introduced as fibers with 1% by the total volume of the mixture. Mechanical and durability tests were conducted for various mixtures of concrete as compressive and flexural strengths, water absorption, ultrasonic pulse velocity, and acid attack. Also, other in-depth analyses were performed on samples of each variant such as X-ray diffraction (XRD), thermogravimetric analysis (DSC-TGA), and scanning electron microscope (SEM). The results show that the addition of glass powder or plastic fibers or a combination of both in concrete improved in the compression and flexural strengths in the long term. The highest compressive strength was obtained in the mix which combines the two wastes about 26.72% of increase compared to the control concrete. The flexural strength increased in the mixture containing the glass powder. Therefore, the mixture with two wastes exhibits better resistance to aggressive sulfuric acid attack, and incorporating glass powder improves the ultrasonic pulse velocity.

• Journal of the Korean Wood Science and Technology
• /
• 제50권6호
• /
• pp.490-498
• /
• 2022

The current study aimed to verify the image segmentation ability of rays in tangential thin sections of conifers using artificial intelligence technology. The applied model was Mask region-based convolutional neural network (Mask R-CNN) and softwoods (viz. Picea jezoensis, Larix gmelinii, Abies nephrolepis, Abies koreana, Ginkgo biloba, Taxus cuspidata, Cryptomeria japonica, Cedrus deodara, Pinus koraiensis) were selected for the study. To take digital pictures, thin sections of thickness 10-15 ㎛ were cut using a microtome, and then stained using a 1:1 mixture of 0.5% astra blue and 1% safranin. In the digital images, rays were selected as detection objects, and Computer Vision Annotation Tool was used to annotate the rays in the training images taken from the tangential sections of the woods. The performance of the Mask R-CNN applied to select rays was as high as 0.837 mean average precision and saving the time more than half of that required for Ground Truth. During the image analysis process, however, division of the rays into two or more rays occurred. This caused some errors in the measurement of the ray height. To improve the image processing algorithms, further work on combining the fragments of a ray into one ray segment, and increasing the precision of the boundary between rays and the neighboring tissues is required.