• 한국도로학회논문집
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• 제15권6호
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• pp.93-101
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• 2013

PURPOSES : The rumble strip installed at the highway near the tollgate has the purpose to reduce the vehicle velocity or prevent sleepiness by awakening people to the danger. These rumble strip has different vibration decibel from the rumble strip shapes, resulting in some fatigue damage to human because a driver suffers from a lot of stress and displeasure. In this connection, the objective of this paper is to analyze the vibration decibel perceived by a driver in the vehicle under some conditions. METHODS : The vibration decibel conveyed from the tire can be analyzed. The frequency analysis methods were used according to DFT (Discrete Fourier Transform) analysis, FFT (Fast Fourier Transform) analysis, CPB (Constant Percentage Bandwidth) analysis. But the frequency analysis method in this paper is the 1/24 OCT(Octave) band analysis because of the convenience of the analysis and the overall vibration amplitude along the frequency. RESULTS : By using the results of the vibration decibel after analyzing the 1/24 OCT band analysis, these results can be compared from some conditions (e.g., rumble strip shape, uniform velocity of a vehicle, road condition, mass of a vehicle). As a result, the numerical values of decibel are not directly proportional to the vehicle velocity. CONCLUSIONS : At the condition that a vehicle is passing by the rumble strip, the value of a vibration decibel at the rumble strip of the cylinder shape is smaller than the rumble strip of rectangular shape regardless of the rumble strip depth and width. At the mass condition, the more a vehicle is massive, the more the vibration decibel increases. At the road condition, the vibration decibel at the wet road is smaller than the value at dry road condition.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.365-365
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• 2010

Similar to the superhydrophobic surfaces of lotus leaf, water strider leg is attributed to hierarchical structure of micro pillar and nano-hair coated with low surface energy materials, by which water strider can run and even jump on the water surface. In order to mimick its leg, many effort, especially, on the fabrication of nanohairs has been made using several methods such as a capillarity-driven molding and lithography using poly(urethane acrylate)(PUA). However most of those effort was not so effective to create the similar structure due to its difficulty in the fabrication of nanoscale hairy structures with hydrophobic surface. In this study, we have selected a low surface energy polymeric material of polytetrafluoroethylene (PTFE, or Teflon) assisted with surface modification of CF4 plasma treatment followed by hydrophobic surface coating with pre-cursor of hexamethyldisiloxane (HMDSO) using a plasma enhanced chemical vapor deposition (PE-CVD). It was found that the plasma energy and duration of CF4 treatment on PTFE polymer could control the aspect ratio of nano-hairy structure, which varying with high aspect ratio of more than 20 to 1, or height of over 1000nm but width of 50nm in average. The water contact angle on pristine PTFE surface was measured as approximately $115^{\circ}$. With nanostructures by CF4 plasma treatment and hydrophobic coating of HMDSO film, we made a superhydrophobic nano-hair structure with the wetting angle of over $160^{\circ}C$. This novel fabrication method of nanohairy structures has been applied not only on 2-D flat substrate but also on 3-D substrates like wire and cylinder, which is similarly mimicked the water strider's leg.

• Smart Structures and Systems
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• 제18권3호
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• pp.405-423
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• 2016

In this study, the feasibility of using telecommunication single-mode optical fiber (SMF) as a distributed fiber optic strain and crack sensor was evaluated in concrete pavement monitoring. Tensile tests on various sensors indicated that the $SMF-28e^+$ fiber revealed linear elastic behavior to rupture at approximately 26 N load and 2.6% strain. Six full-scale concrete panels were prepared and tested under truck and three-point loads to quantify the performance of sensors with pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA). The sensors were protected by precast mortar from brutal action during concrete casting. Once air-cured for 2 hours after initial setting, half a mortar cylinder of 12 mm in diameter ensured that the protected sensors remained functional during and after concrete casting. The strains measured from PPP-BOTDA with a sensitivity coefficient of $5.43{\times}10^{-5}GHz/{\mu}{\varepsilon}$ were validated locally by commercial fiber Bragg grating (FBG) sensors. Unlike the point FBG sensors, the distributed PPP-BOTDA sensors can be utilized to effectively locate multiple cracks. Depending on their layout, the distributed sensors can provide one- or two-dimensional strain fields in pavement panels. The width of both micro and major cracks can be linearly related to the peak strain directly measured with the distributed fiber optic sensor.

• 수산해양기술연구
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• 제54권4호
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• pp.271-278
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• 2018

In this study, the conventional cylinder-shaped lower bar on the canvas was modified and its performance was tested to improve the opening force of the stow net on anchor. The improved new lower bar used in the test is consisted of 13 flat bars with a length of 1.8 m, a width of 0.075 m and a thickness of 4 mm, and a pipe with a length of 2.0 m and a diameter of 50 mm. A stow net with the improved lower bar and a stow net with an existing lower bar were installed underwater and their trajectories for 21 hours were examined. To confirm their trajectories, GPS loggers were attached to the buoys on the left and right canvases and the buoy of the hauling rope. As a result of the test, the rotation of the gear with the improved bar was smoother than that with the existing bar. As a result of comparing the changes in the interval of the buoys attached to the canvas after the low and high tide, the buoy spacing of the gear with the improved bar is wider than that of the conventional gear; moreover, the larger the interval, the smoother the rotation of the fishing gear was. Therefore, it is considered that using the improved lower bar can enhance the performance of the stow net.

• 천문학논총
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• 제36권3호
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• pp.65-78
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• 2021

Jagyeokru, an automatic striking water clock described in the Sejong Sillok (Veritable Records of King Sejong) is essentially composed of a water quantity control device and a time-signal device, with the former controlling the amount or the flow rate of water and the latter automatically informing the time based on the former. What connects these two parts is a signal generating device or a power transmission device called the 'Jujeon' system, which includes a copper rod on the float and ball-racked scheduled plates. The copper products excavated under Gongpyeong-dong in Seoul include a lot of broken plate pieces and cylinder-like devices. If some plate pieces are put together, a large square plate with circular holes located in a zigzag can be completed, and at the upper right of it is carved 'the first scheduled plate (一箭).' Cylinder-like devices generally 3.8 cm in diameter are able to release a ball, and have a ginkgo leaf-like screen fixed on the inner axis and a bird-shaped hook of which the leg fixes another axis and the beak attaches to the leaf side. The lateral view of this cylinder-like device appears like a trapezoid and mounts an iron ball. The function of releasing a ball agrees with the description of Borugak Pavilion, where Jagyeokru was installed, written by Kim Don (1385 ~ 1440). The other accounts of Borugak Pavilion's and Heumgyeonggak Pavilion's water clocks describe these copper plates and ball releasing devices as the 'Jujeon' system. According to the description of Borugak Pavilion, a square wooden column has copper plates on the left and right sides the same height as the column, and the left copper plate has 12 drilled holes to keep the time of a 12 double-hours. Meanwhile, the right plate has 25 holes which represent seasonal night 5-hours (Kyeong) and their 5-subhours (Jeom), not 12 hours. There are 11 scheduled plates for seasonal night 5-hours made with copper, which are made to be attached or detached as the season. In accordance with Nujutongui (manual for the operation of the yardstick for the clepsydra), the first scheduled plate for the night is used from the winter solstice (冬至) to 2 days after Daehan (大寒), and from 4 days before Soseol (小雪) to a day before the winter solstice. Besides the first scheduled plate, we confirm discovering a third scheduled plate and a sixth scheduled plate among the excavated copper materials based on the spacing between holes. On the other hand, the width of the scheduled plate is different for these artifacts, measured as 144 mm compared to the description of the Borugak Pavilion, which is recorded as 51 mm. From this perspective, they may be the scheduled plates for the Heumgyeonggak Ongru made in 1438 (or 1554) or for the new Fortress Pavilion installed in Changdeokgung palace completed in 1536 (the 31^st year of the reign of King Jungjong) in the early Joseon dynasty. This study presents the concept of the scheduled plates described in the literature, including their new operating mechanism. In addition, a detailed model of 11 scheduled plates is designed from the records and on the excavated relics. It is expected that this study will aid in efforts to restore and reconstruct the automatic water clocks of the early Joseon dynasty.

• 농업과학연구
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• 제4권2호
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• pp.215-228
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• 1977

양질 옥수수 육성을 위한 우량한 유전자원을 공급하기 위하여 전국적으로 수집한 총 948개의 재래종 옥수수 이삭에 대하여 주요 형태적 특성을 조사하였던바, 다음과 같은 몇가지 결과를 얻었다. 1) 이삭형태 : 한국 재래종 옥수수의 이삭형태는 IV형 II형 III형 I형의 순으로 구성되었으며, 옥수수의 주산지인 북동부 산악지대에서는 원통형 내지는 원통형에 가까운 형태의 이삭이 많았고, 옥수수가 소규모로 재배되고 있는 남부 평야지대에서는 원추형 내지는 원추형에 가까운 형태의 이삭이 많았다. 2) 입색 : 전국 10개 지역에서 수집된 모든 재래종 옥수수 이삭 가운데서 단색립을 가진 이삭이 54.4%, 가지 색갈의 입색이 혼합된 이삭이 39.0%이없고 세가지 이상의 입색을 가진 이삭이 6.6%이었다. 북부산간지대에서는 이삭의 색갈은 백색혹은 백색과 다른 색갈이 혼합된 것이 많았고, 그 밖의 다른 지역에서는 이삭이 색갈이 노란색 혹은 노란색과 다른 색갈이 혼합된 것이 많았다. 3) 마치성 : 수집된 재래종 옥수수 가운데 불과 4.3%만이 마치종 이었고 나머지는 경립종이었다. 마치종은 외국 옥수수 품종이 도입된 북부 지방에서 수집되었다. 4) 이삭열수 : 수집된 재래종 옥수수의 이삭열수는 12열 내지 16열이 대부분이었고, 수집된 지역에 따라 분류된 이삭열수 사이에는 큰 차이가 없었다. 여하튼, 이삭열수는 입의 크기에 밀접한 관계가 있는 것으로 나타났다. 예를 들면, 이삭열수가 24개나 되는 이삭의 입은 그 크기가 매우 작았다. 5) 입질 : 수집된 재래종 옥수수의 70.9%가 경질립이었고, 연질립은 26.0% 그리고 중간형이 3.1%이었다. 옥수수의 주산지인 A지역과 I지역에서 경질 옥수수가 더 많이 수집 되었다. 6) 폭열종과 찰옥수수 : 수집된 재래종 옥수수를 보면 폭열종 옥수수는 I지역(울릉도)를 제외하고는 고르게 분포되어 있었고, 찰옥수수는 북부 산간지방에서 많았다. 7) 이삭길이 : 수집된 재래종 옥수수의 평균 이삭길이는 13cm이었고, A지역과 I지역에서 수집된 옥수수의 길이가 다른 지방의 것보다 길었다. 8) 이삭직경 : 수집된 재래종 옥수수의 평균 이삭직경은 3.3cm이었고, A지역과 I지역에서 수집된 옥수수의 이삭직경이 다른 지방의 것보다 컸다. 9) 입길이, 입폭, 입깊이 : 수집된 재래종 옥수수의 평균 입길이, 입폭, 입깊이는 각각 0.82cm, 0.42cm 그리고 0.78cm 이었다. A 지역과 I 지역에서 수집된 옥수수의 입의 다른 지역에서 수집된 옥수수의 입보다 컷다. 10) 이삭 무게 : 수집된 재래종 옥수수의 평균 이삭무게는 평균 58.04gr 이었으며 A 지역과 I 지역에서 수집된 것이 현저히 무거웠다. 가장 무거운 이삭의 무게는 330gr 이었고 가장 가벼운 이삭의 무게는 5gr 이었다. 11) 이삭당 입중 및 100입중 : 수집된 재래종 옥수수의 이삭당 입중은 평균 47.07gr 이었고 100입중은 평균 15.07gr 이었다. 이삭당 입중 및 100입중은 A 지역과 I 지역에서 수집된 것이 더 무거웠다.

• 한국안광학회지
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• 제12권3호
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• pp.83-87
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• 2007

본 연구는 안질환이 없고 양안시 기능이 정상인 20대에서 50대 사이의 근시성 난시를 가지고 있는 남, 녀 대학생 57명(114 eye)을 대상으로 난시안의 굴절이상도를 완전교정한 상태에서 교정축 만을 $5^{\circ}$, $10^{\circ}$, $15^{\circ}$ 회전하여 완전교정상태와의 시력상태를 비교 분석하였다. 난시 교정안경 착용자의 30.8%가 난시축이 정확하게 교정되지 않은 안경을 착용하고 있었으며, 난시안을 정확하게 교정한 후의 시력과 난시량을 완전교정하고 교정축을 $5^{\circ}$, $10^{\circ}$, $15^{\circ}$ 이동한 시력을 비교한 결과 한 줄 이상의 시력 감소가 나타나는 눈이 각각 56.1%, 84.2%, 93.8%로 조사되었다. 교정축을 완전교정 했을 때와 축이 이탈했을 때와의 시력감소의 폭은 이탈 각도가 클수록 크다는 것을 알 수 있었으며, 난시 교정축의 이탈 각도에 따른 평균 시력변화는 완전교정 했을 때와 비교할 때 $5^{\circ}$에서는 0.94, $10^{\circ}$에서는 0.87, $15^{\circ}$에서는 0.79로 조사되었다. 또한, 완전 교정축에서 $5^{\circ}$ 이탈했을 때는 문자시표에서는 약 한 줄 정도의 시력차이가 있었고, $10^{\circ}$이탈 했을 때는 약 1.8줄 정도의 시력차이가 있었고, $15^{\circ}$ 이탈 했을 때는 약 2.6줄 정도의 차이가 발생하는 것으로 조사되었다. 즉, 난시 교정안경의 교정축이 이탈되었을 경우 시력감소가 발생하는 것을 확인할 수 있었고, 난시안의 교정축 이탈은 안정피로를 유발할 수 있으므로 시력검사 과정에서 정확한 난시축의 교정은 중요한 요소이므로 처방을 토대로 한 난시 교정안경 조제가공 후 교정축의 정확도 확인을 반드시 실시하여 축 오류를 최소화해야 한다고 사료된다.

• 대한치과기공학회지
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• 제30권2호
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• pp.47-56
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• 2008

This is a research for thickness change of denture base according to the shape of sprue & investment position of denture base in flask when injecting polyamid base resin for flexible partial denture as a part of study for Valplast among the flexible partial denture with a nylon base. It has been introduced several kinds of flexible partial denture product with a nylon base, but Valplast is the most widely used product among them. Valplast has been the most generally used material today since developed in 1950s in the United States as a material for flexible partial denture. Valplast is much more aesthetic than general metal-acrylic partial denture due to its translucent pink color and biocompatibility in terms of material characteristic. It keeps its flexibility for a long time after production, imposes a less burden on the teeth used as abutment, and it can be easily insert and remove due to its particular suppleness. Moreover, it is felt like real teeth more than metal-acrylic partial denture when being put in and takes alveolar bone under good protection since it receives occlusal force equally under the denture base. The most outstanding feature of Valplast is flexibility. The extent of its flexibility is determined by width & thickness of denture base. Considering general working procedure of Valplast, it can be seen that the thickness of denture base formed out of wax is increasing by the pressure while injecting resin. This research is to decide and test on the thickness increasing of Valplast by injecting pressure and the hypothesis upon that and is to prepare the basis estimating the increasing extent of thickness of denture base on the basis of the test result. In this test, it is expected occlusal malposition & thickness increasing of denture base by injecting pressure according to 4 kinds of test data which are to select 3 types of sprue method settling the forefront position at which the test material of fixed standard can be invested and to position the test material at the rearmost part keeping the minimum distance to set sprue. For 4 kinds of injecting test by investment position & sprue type, 20 test materials, 5 for each test were produced and a pressure of 1,180Kg was given with automatic injector of air cylinder type. The results are as follows: 1. For the amount of thickness increasing of denture base by investment position, the thickness of front investment is less increasing than the one of rear investment. 2. For the amount of thickness increasing of denture base by sprue type, the thickness of straight decompression sprue type which can absorb the injecting pressure after injecting polyamide base resin is less increasing than the other sprue types.

• 한국약용작물학회지
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• 제13권1호
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• pp.21-29
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• 2005

경남지역의 자생 둥굴레속 47개 수집종의 유연관계를 분석하기 위한 기초자료로서 수집종의 생장 몇 형태 관련 형질, 잎마름병 감염정도, 이들 형질간 상관관계를 분석하였던 바 그 결과는 다음과 같다. 1. 초장은 산둥굴레에서 가장 길었던 반면, 용둥굴레에서 가장 짧았다. 한편 줄기의 생장형태는 직립형을 포함한 3개군으로, 줄기색깔은 녹색을 포함한 3개군으로 분류하였다. 2. 염의 형태로는 타원형을 포함한 5개군으로, 엽병은 존재 유무로부터 2개군으로, 엽병의 색깔은 녹색을 포함한 3개군으로 분류되었으며, 그 중에 특이하게 피침 형태로 엽연이 자색인 1개종이 수집되었다. 3. 꽃은 화형이 항아리형, 통형, 조롱박형의 3개군으로, 화색은 흰색을 포함한 3개군으로 분류되었으며, 특별하게 조롱박형인 1개 수집종은 연녹색을 띄고 있었다. 화사는 실린더형과 편평형으로, 화경의 색깔은 자색을 포함한 4개군으로 분류되었으며, 포의 존재 유무와 형태에 따라 4개군으로 분류하였다. 4. 과실은 둥근형 등 3개군으로 분류되었으며, 백과중은 둥굴레에서 가장 무거웠던 반면, 용둥굴레에서 가장 가벼웠다. 5. 둥굴레 잎마름병에 대한 저항성이 아주 강한 것은 2종, 이병율이 7% 이하인 것은 7개종으로 조사되어서 근경수량을 증대할 수 있는 저항성 유전자원이 자생하고 있음을 알 수 있었다. 6. 제형질의 상관관계에서 근경수량과 관련된 근경중은 초장, 경직경, 엽수, 엽장, 엽폭, 지하경 직경과 정의상관을 보였으나 근경수량에 가장 큰 영향을 미치는 잎마름병 이병율은 초장, 경직경, 엽수, 엽장, 백립중, 근경중, 지하경 직경과 부의상관을 보였다.