• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.221-227
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• 2013

In this paper, Satellite DMB/WiBro antenna and PCS/WiBro antenna improving indoor coverage for mobile services are designed and fabricated. Satellite DMB/WiBro bands repeater antenna and PCS/WiBro bands repeater antenna are proposed as a simple radiator with loading capacitor to generate LHCP(Left Hand Circular Polarization). The proposed antenna for Satellite DMB/WiBro and PCS/WiBro bands communication are fabricated by copper plate uploader type and substrate uploader type. The designed and fabricated antenna has a bandwidth of 70MHz at 1.816GHz~1.886GHz and bandwidth of 107MHz at 2.247GHz~2.354GHz. Maximum gain of radiation pattern was up to 5dBi.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1192-1198
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• 2008

In this paper, the vibration and shock of an HDD car-holder are reduced through vibration analysis and a structural modification. In order to identify the exciting frequency components of vibration and shock, vibration signals are measured and analyzed from the wind shield or dashboard. In addition, the modal test for the current HDD car-holder is performed to investigate the dynamic characteristics of the car-holder. From these experiments, it is found that the exciting frequencies coincide to the natural frequencies of the car-holder. For the purpose of avoiding resonance, some FEM simulations are carried out and then structural modifications are made for the car-holder. Based on the results of simulations, a prototype of new car-holder are manufactured and tested to demonstrate the reduction of vibration and shock. It is verified by the test that a considerable amount of vibration and shock are reduced.

• Journal of Korean Society of Forest Science
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• v.22 no.1
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• pp.49-62
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• 1974

1. In the comparison of survival ratio among three different methods(bark graft, veneer graft, root graft), bark graft showed the highest survival ratio and root graft was the lowest. It was shown to be significant at the level of 5% in the analysis of variance for the results. It was able to be supposed that one of the main causes for the results was the different amounts of ferric tannic acid which was formated owing to the reaction of grafting knife with tannic acid oozing from cutting faces of the tree. In juvenile tissue graft, the survival ratio of inverted radicle graft was a little higher than that of juvenile stem graft, but there was no significant difference between two methods in analysis of variance. 2. The most hairs of chestnut tree leaves were recognized as stellates on the most part of leaves except for venation. The number of rays in the stellates was ranged from 4 to 8 generally. It was shown to be highly significant differences at the level of 1% among the each race growing at the similar environmental condition in the length of ray and the distributed ratio of the stellates having different ray number. 3. Excepting for the basal width of serration there were no significant differences between $Imakita_1$, $Imakita_2$ as well as between $Teteuchi_1$, $Teteuchi_2$ at the each point of experimental items in this study. Such results made this study more useful. 4. Among the races that were growing in the similar environmental condition, there were highly significant differences at the level of 1% in the length and the width of serration. 5. The rolling of hair, the angle of serration from the leaf margin, the existence of lateral vein in the serration, the intrusion of main vein into the serration and the width of main vein were observed to be somewhat useful as the subsidiary methods for the identification of chestnut races.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.803-809
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• 2018

Generally, the gap-and-sag method is used in the shipbuilding stage before coupling the shafts to check whether they are installed at the same position as designed and derived from shaft alignment calculation. The primary installed propeller shaft becomes a reference point, the position of the remaining shafts are sequentially determined through the gap-and-sag value derived from the deflection and deflection angle at each shaft flange by own weight. If the reference point varies against the design value, it would have a series of effects on the installation of the remaining shafts. Moreover, after coupling the shafts, even if the bearing reaction forces derived from measurement are satisfied by the allowable limit range, consequently it might have an adverse effect on the stability of the shafting system by not being able to estimate the relative slope angle between the propeller shaft and the after-stern tube bearing. In this paper, to deal with above-mentioned phenomenon, the theoretical calculations related to designing an effective support point of the aft stern tube bearing and analysis by measurement is conducted through a case of open-up inspections. Based on this, a shaft installation guideline is proposed to minimize the misalignment related to preventing wiping damage of the after-stern tube bearing.

• Journal of Korean Society of Forest Science
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• v.57 no.1
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• pp.39-44
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• 1982

These studies were carried out to know the variation of needle characteristics of Abies Koreana distributed in Korea. The results are summarized as follows. The differences of needle length and number of stomata row among the population were shown one percent level, but not in each individual tree. Correlations coefficients between the D.B.H. and needle length or needle width of mother trees were not correlated all populations respectively. It was found that correlation coefficient between needle length and needle width was positive in two populations. of Mt. Doukyou and Mt. Hanla, but it was not in Mt Jiri. Correlation coefficient between needle length and the number of stomata row positive correlation in Mt. Doukyou. Correlation coefficient between needle width and the number of stomata row was shown positive in all populations, but it was not that correlation coefficient between needle width and density of serrations, and between number of stomata row and density of serrations. The coefficients of variations were shown higher density of serration than needle length, needle width and stomata row.

• Korean Journal of Plant Resources
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• v.20 no.4
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• pp.336-341
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• 2007

This study was carried out to investigate geographic variation in needle characteristics of Pinus densiflora, one of the most economically important tree species in Korea. Needles were collected from 35 natural populations and their morphological and anatomical characteristics were studied. ANOVA showed statistically significant differences among populations as well as among individuals within populations in needle length, needle width, number of stomata row, density of stomata in $0.25mm^{2}$, number of serrations in 0.5mm, and number of resin ducts. In all these traits, variance components among individuals within populations were larger than those among populations. The density of stomata in $0.25mm^{2}$ increased as the latitudes and elevations of the populations increased, while the number of serrations in 0.5mm decreased as the decrease of latitudes and elevations. The number of resin ducts was higher in inland populations than in coastal populations. The resin duct index appeared to be higher in western populations than in eastern populations. Cluster analysis based on morphological characteristics divided populations into three groups. The third group was composed of populations selected from the Taebaek mountains. The number of serrations in 0.5mm of this group was lower than that of other two groups, while the density of stomata in $0.25mm^{2}$ was higher.

• Korean Journal of Plant Resources
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• v.12 no.1
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• pp.50-61
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• 1999

The leaf morphological and anatomical characters about 17 taxa of Aster and its allied taxa were investigated to estimate taxonomic values. Leaf shapes of the treated taxa were divided into five types; elliptic, spathulate, lanceolate, linear, ovatodeltoid. These types were fixed in same taxa, but variable among different taxa, therefore useful as taxonomic character. Leaf margins were divided into four types; entire, serrate, dentate, incised, these types were invariable in most taxa, but variable among individual in same taxa such as Kalimeris incise, Aster spathulifolius. The size and shape of leaf epidermal cell, the size and distributional numbers per 10$\textrm{mm}^2$ of stomata, deposit feature of cuticle were not distinguished clearly from treated taxa, but presence of stomata on adaxial surface, size and distributional numbers per 10$\textrm{mm}^2$ of stomata were useful taxonomic characters in some taxa such as Gymnaster koraiensis, Aster altaicus var. uchiyamae, Aster tripolium, Heteropappus arenarius. The leaf trichomes were divided into five types by basic form, sculpturing on their outer surface and cell arrangement; uniseriate granulate conical type, uniseriate psilate conical type, uniseriate psilate filiform type, globular type, biseriate vesicular capitate type. In spite of various habitat, basic morphology of trichomes were not changed, therefore, it was thought to be good taxonomic character.

• International Journal of Highway Engineering
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• v.11 no.1
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• pp.135-144
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• 2009

The purpose of this study is to develop a simple and rational crack evaluation system using Marshall tester. Fracture energy were used as a parameter to evaluate the crack resistance of asphalt mixtures. Marshall tester basically measures the vertical deformation obtained from the linear variable differential transformer(LVDT) attached on the specimen's exterior, which can cause a measurement error due to the local deformation near the loading head. Therefore, the validity of the measurement system of Marshall tester should be tested to use it in calculation of fracture energy. Two types of indirect tensile strength tests were performed using four types of asphalt mixtures at two temperature conditions. From the tests, it was shown that local deformation near the loading head had not occurred before a specimen was fractured, so that it did not cause the measurement error of fracture energy. And also from the statistic analysis, the coefficient of variation of vertical deformation measurements obtained on specimen's exterior is less than 15%. Thus, vertical deformation measurements obtained on the specimen's exterior can be used in crack evaluation system using Marshall tester.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.12a
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• pp.49-49
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• 2020

본 연구는 호랑버들과 갯버들 교잡종의 잎 형태적 특성을 국내 자생종인 호랑버들, 갯버들과 비교하였다. 호랑버들 35개체, 갯버들 35개체, 교잡종 100개체에서 잎을 채취하여 잎의 길이와 너비, 엽저와 엽두 각도, 잎자루 길이와 너비, 탁엽의 길이와 너비, 잎 두께 등 총 17개의 잎 형태적 특성을 분석한 결과, 엽두 각도와 탁엽의 길이를 제외한 15개의 특성에서 세 분류군이 유의한 차이를 나타내었다. 교잡종의 잎 길이와 너비의 비는 갯버들, 교잡종, 호랑버들 순으로 크게 나타나 교잡종의 잎의 형태는 피침형인 갯버들과 타원형인 호랑버들 사이 중간 형태로 나타났다. 교잡종의 잎의 너비, 엽저 각도, 잎자루의 길이와 너비, 탁엽의 길이와 너비는 호랑버들과 갯버들의 중간 형태를 나타내었으며, 탁엽의 거치 개수는 교잡종이 호랑버들과 갯버들보다 많은 특성이 나타났다. 잎 뒷면 단위면적당 털의 개수 또한 교잡종이 호랑버들과 갯버들보다 많은 특성을 나타냈다. 세 분류군 간 잎 형태적 차이를 구명하기 위해 유의한 차이를 보인 15개의 변수를 이용하여 주성분분석을 실시한 결과 고유값이 1 이상인 제 1, 2, 3, 4주성분이 전체 분산의 68.2%를 설명하였다. 제 1주성분은 잎의 너비, 잎의 1/3 아랫부분 너비, 잎의 1/3 윗부분 너비, 잎자루의 길이, 잎의 길이로 잎의 크기와 관련이 있는 특성들이 높은 상관관계를 나타내었고, 제 2주성분은 엽맥의 수, 잎자루의 너비와 높은 상관관계를 나타내었다. 제 3주성분은 탁엽의 거치 개수, 탁엽의 너비로 탁엽의 특성과 관련이 있는 특성들이 높은 상관관계를 나타내었으며, 제 4주성분은 잎의 두께와 높은 상관관계를 나타내었다. 주성분분석 결과 호랑버들과 갯버들 교잡종의 잎 특성은 호랑버들보다 갯버들과 가까운 것으로 나타났다. 잎의 형태적 특성으로 세 분류군을 구별하기 위해 정량형질을 이용한 판별분석 결과 교잡종 중 대부분(93.3%)이 호랑버들, 갯버들과 구별되었다. 일부 교잡종 개체(6.7%)가 갯버들로 오분류되었지만, 잎의 정성적 특성인 잎의 거치와 측맥의 특성을 고려한 결과 모든 개체가 교잡종으로 구분되었다. 따라서 호랑버들과 갯버들의 교잡종은 잎의 형태적 특성이 부모종인 호랑버들, 갯버들과 다른 독특한 형태를 가진 것으로 나타났다.

• Journal of the KSME
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• v.16 no.4
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• pp.12-18
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• 1976

기계 및 구조물들이 등진폭하중만을 받는 경우는 극히 드물어서 대부분이 진폭과 주파수가 불규 칙하게 변하는 하중을 받는다. 실하중이력이 불규칙(random)한 모양을 갖는 것은 비행기, 자동차, 선박 등의 많은 기구물들이 공기의 터블런스, 거치론 도로표면 및 대양의 파도와 같이 random한 주위환경에 접하기 때문이다. 이 random한 환경과 구조물의 탄성성질들로 인해서 구조물로부터 측정된 하중응답신호들(응신율,변위 혹은 가속도)은 건폭과 주파수가 random하게 변하는 특정한 형태의 파형을 갖는다. 현금 우리나라에 이 방면의 연구가 활발하지 못하여 complex load history가 피로에 미치는 영향과 이에 관련된 피로시험들을 간략히 소개한다.