• Journal of the Korean Geotechnical Society
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• v.22 no.11
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• pp.47-54
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• 2006

Shear wave velocity of uncemented soil can be expressed as the function of effective stresses when capillary phenomena are negligible. However, the terms of effective stresses are divided into the direction of wave propagation and polarization because stress states are generally anisotropy. The shear wave velocities are affected by ${\alpha}$ parameters and ${\beta}$ exponents that are experimentally determined. The ${\beta}$ exponents are controlled by contact effects of particulate materials (sizes, shapes, and structures of particles) and the ${\alpha}$ parameters are changed by contact behaviors among particles, material properties of particles, and type of packing (i.e., void ratio and coordination number). In this study, consolidation tests are performed by using clay, mica and sand specimens. Shear wave velocities are measured during consolidation tests to investigate the stress-induced and inherent anisotropies by using bender elements. Results show the shear wave velocity depends on the stress-induced anisotropy for round particles. Furthermore, the shear wave velocity is dependent on particle alignment under the constant evvective stress. This study suggests that the shear wave velocity and the shear modulus should be carefully estimated and used for the design and construction of geotechnical structures.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.610-620
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• 2022

An acoustic vector sensor can simultaneously receive vector quantities, such as particle velocity and acceleration, as well as acoustic pressure at one location, and thus it can be used as a single input multiple output receiver in underwater acoustic communication systems. On the other hand, vector signals received by a single vector sensor have different channel characteristics due to the azimuth angle between the source and receiver and the difference in propagation angle of multipath in each component, producing different communication performances. In this paper, we propose a channel parameter-based weighting method to improve the performance of an acoustic communication system using a single vector sensor. To verify the proposed method, we used communication data collected from the experiment conducted during the KOREX-17 (Korea Reverberation Experiment). For communication demodulation, block-based time reversal technique which is robust against time-varying channels were utilized. Finally, the communication results showed that the effectiveness of the channel parameter-based weighting method for the underwater communication system using a single vector sensor was verified.

• International Journal of Computer Science & Network Security
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• v.23 no.4
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• pp.55-68
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• 2023

In recent years, the Television White Space (TVWS) has attracted the interest of many researchers due to its propagation characteristics obtainable between 470MHz and 790MHz spectrum bands. The plenty of unused channels in the TV spectrum allows the secondary users (SUs) to use the channels for broadband services especially in rural areas. However, when the number of SUs increases in the TVWS wireless network the aggregate interference also increases. Aggregate interferences are the combined harmful interferences that can include both co-channel and adjacent interferences. The aggregate interference on the side of Primary Users (PUs) has been extensively scrutinized. Therefore, resource allocation (power and spectrum) is crucial when designing the TVWS network to avoid interferences from Secondary Users (SUs) to PUs and among SUs themselves. This paper proposes a model to improve the resource allocation for reducing the aggregate interface among SUs for broadband services in rural areas. The proposed model uses joint power and spectrum hybrid Firefly algorithm (FA), Genetic algorithm (GA), and Particle Swarm Optimization algorithm (PSO) which is considered the Co-channel interference (CCI) and Adjacent Channel Interference (ACI). The algorithm is integrated with the admission control algorithm so that; there is a possibility to remove some of the SUs in the TVWS network whenever the SINR threshold for SUs and PU are not met. We considered the infeasible system whereby all SUs and PU may not be supported simultaneously. Therefore, we proposed a joint spectrum and power allocation with an admission control algorithm whose better complexity and performance than the ones which have been proposed in the existing algorithms in the literature. The performance of the proposed algorithm is compared using the metrics such as sum throughput, PU SINR, algorithm running time and SU SINR less than threshold and the results show that the PSOFAGA with ELGR admission control algorithm has best performance compared to GA, PSO, FA, and FAGAPSO algorithms.

• Journal of Bio-Environment Control
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• v.32 no.3
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• pp.210-216
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• 2023

Conventionally, the seeds of Rehmannia glutinosa (Gaertn.) Libosch. ex Steud. have been directly sown at the field without using the plug seedling method. Plug seedlings have the advantage of promoting germination and convenient transplanting. However, there is little information about propagation of R. glutinosa using the plug seedling method. This study was conducted to investigate the optimal seed rhizome length, diameter, and sowing direction of R. glutinosa for establishing the plug seedling method. Seed rhizome length and diameter were separated by 1, 2, 3 cm and 0.3-0.5, 0.6-1.0, 1.1-1.5 cm, respectively. And seed rhizomes were sown in vertical and horizontal directions. The survival rate in 1 cm length of seed rhizomes was lower than in other treatments. The leaf length, leaf width, number of leaves, SPAD, leaf area, and fresh and dry weights of shoot and roots were the greatest in 3 cm length of seed rhizomes. As the seed rhizome diameter decreased, the growth characteristics of R. glutinosa tended to increase. When R. glutinosa was sown horizontal direction, the leaf length, leaf width, number of leaves, and leaf area were significantly higher than in the vertical direction. In conclusion, when sowing seed rhizome in a plug tray, using a length of 3 cm, a diameter of less than 1 cm, and sowing in a horizontal direction is considered an appropriate sowing method for R. glutinosa.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3B
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• pp.315-321
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• 2008

Recently, in the light of environments and utilization, countermeasures to preserve beaches in coastal area are required without depending on such as jetties and breakwaters. The necessity of integrated sand management including not only coastal sediment but also sediment discharge from hinterland rivers is increased so as to establish long-term counterplan for sediment transport. In this regard, the following subjects are examined in this study; efficient ways for discharged sand to be transported from a river to the neighboring coast, the river terrace occurrence and its growth at the river delta, measures to improve storage efficiency of the discharged sand and measures to prevent the sand resources from being discharged into the deep sea during flooding. In recent, A jetty of 260 m length was constructed at Namdae River mouth in the year of 2005 as a countermeasure against the occurrence of sand-bar at river mouth and its close. In this study, a series of numerical experiments were carried out to investigate the characteristics of sediment transport and morphological change due to the construction of jetty at the entrance of Namdae River mouth. Firstly, The sand discharge from Namdae River is quantified by one-dimensional numerical analysis assuming the mixed sand of three different particle diameters. Then, in order to understand the transport behavior of the sand discharge from river and river mouth phenomena the numerical experiments were then conducted to examine the flow behaviors of river efflux and wind generated circulations in coastal area. And, after establishing the numerical model system, which predicts the sea bed changes obtained from the flux model combining with the wave propagation, wave-induced currents and sediment transport models, the sediment transport in the vicinity of Namdae River mouth is analyzed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1C
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• pp.11-20
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• 2009

A new alternative method based on HWAW method to detect underground anomaly was introduced. The location of underground anomaly can be estimated by using 2-dimensional image of phase velocity image with position and wavelength based on distortion phenomena of surface wave due to underground anomaly. Overall procedure of proposed method such as field testing, signal processing and interpretation of the result was introduced. Numerical verification study was performed by using various ground models containing underground anomaly. According to the condition of anomaly, the propagation and reflection characteristics of surface wave were different and this could be more easily shown in the image of phase velocity. Some rules of distortion phenomena were found and these become clues for estimating underground anomaly in interpreting real field data. Field verification tests were performed with conventional geophysical methods such as DC resistivity method and GPR. Though field condition is not homogeneous like numerical models, similar distortion phenomena were found in the testing results and estimated location of underground anomaly was agreed well with the results of another geophysical methods.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.08a
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• pp.25-25
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• 2020

산초나무(Zanthoxylum schinifolium Siebold & Zucc.)는 운향과(Rutaceae)에 속하는 낙엽활엽관목으로 주로 열매, 잎, 줄기는 식·약용으로 이용한다. 최근 산초나무 부위별 추출물에서 항산화활성, 항염증효과, 미백효과 등에 관한 연구가 이루어지면서 산초나무의 가치가 더욱 증가하고 있다. 본 연구는 산초나무의 효율적인 유·무성 증식법을 구명하기 위해 종자 처리에 따른 발아특성, 생장조절물질 처리에 따른 가지삽목과 뿌리삽목의 발근특성을 조사하였다. 산초나무 종자는 3개월간 저온습사저장(종자:모래=1:1, -4℃)을 실시할 경우 약 64.0%가 발아하였다. 습사저장된 종자를 파종 직전에 GA3를 이용하여 0, 500, 1,000 및 2,000ppm 농도에서 처리한 결과 각 처리구별 발아율은 유의한 차이를 나타내지 않았다(F=1.556, p=0.260). 다만, 500ppm 농도에서 72.0%가 발아하여 가장 높은 발아율을 보였으며 1,000ppm 이상 처리구에서는 발아율이 다소 감소하는 경향을 나타냈다. 무성증식 방법은 2월 중순에 산초나무 가지삽수와 뿌리삽수를 채취한 후 IBA와 NAA를 각각 0, 500, 1,000 및 2,000ppm 농도로 처리하였다. 가지삽목을 실시한 대부분의 삽수에서 신초가 발생했으나, 발근율은 1.3~6.3%로 현저히 낮았다. 반면, 뿌리삽목은 3개월 후 부정아 발생율이 처리에 따라 58.3~83.3%로 조사되었으며, 발근율은 0~66.7%를 나타나 처리구별 발근율에 유의한 차이가 있었다(F=3.744, p=0.020). IBA 처리가 근삽수의 발근에는 효과적이었으며, 특히 IBA 2,000ppm 처리에서 66.7%의 발근율을 보여 가장 효과적임을 알 수 있었다. 결론적으로, 산초나무의 효율적인 유성증식을 위해서는 종자를 3개월간 저온습사저장하는 것이 효과적이며, 무성증식 방법으로는 가지삽목보다 뿌리삽목을 이용하는 것이 더 효과적인 것으로 판단된다.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2021.04a
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• pp.21-21
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• 2021

주걱댕강나무는 경남 양산의 천성산에서만 생육하는 산림청·국립수목원 지정 희귀식물(Critically Endangered, CR)로 현지외 보전 및 대체 서식지 조성을 위해 번식 특성에 대해 알아보았다. 종자번식의 경우 450립의 종자를 저장방법에 따라 파종한 결과 노천매장 3.56%, 저온건조저장 0.67%, 습사저온저장 0.22%로 발아율이 매우 저조하였으며, 배양토 조건에 따라 직파 실험한 결과 모래 2.44%, 원예용 상토 2.22%, 현지내 산림토 1.11%, 현지외 산림토 0%로 이 또한 발아율이 매우 저조하였다. 삽목번식의 경우 숙지삽은 모래+펄라이트 36.1%, 모래 31.1%, 원예용 상토 20.0%로 나타났으며, 휴면지 삽수의 발근촉진제 처리 효과는 IBA 1,000PPM에서 37.8%, IBA 7,000PPM 30.0%, 무처리 28.9%, IBA 5,000PPM 27.8%의 발근율을 보였고 신초길이, 뿌리의 수, 뿌리 길이는 전반적으로 발근촉진제 처리와 함께 농도가 높아질수록 뿌리 성장이 왕성한 것으로 나타났다. 녹지삽은 모래 80%, 모래+펄라이트 76.7%, 피트모스+마사토 73.3%, 피트모스+펄라이트+버미큘라이트 70.0% 순이며, 왕모래와 왕모래+마사토는 26.7%와 36.7%로 다소 저조하였다. 녹지삽수의 굵기는 4mm이상 구간에서 발근율이 73.3%로 가장 높았으며, 녹지삽수의 길이는 7~8cm 구간에서 80.0%로 가장 높게 나타나 삽수의 굵기가 굵고 8cm내외의 길이가 효율적인 것으로 나타났다. 근삽은 발아율이 88.3~96.7%로 모든 배양토에서 높게 나타났다. 근삽수 직경 7~8mm에서 100%이며 3~4mm 또한 91%로 나타났다. 근삽수 길이는 4~5cm와 10~11cm에서 100%, 6~7cm 88.1%, 8~9cm 94.4%로 나타나 4~5cm를 제외하고는 삽수 길이가 길수록 신초 생장과 발근이 비례하는 것을 확인하였다. 주걱댕강나무는 실생보다 삽목번식이 더 효율적이며, 그 중 근삽이 가장 발근율이 높다. 배양토는 모래 단용구를 제외하고는 평균 95%이상으로 나타났으며, 근삽수는 직경이 굵고 길수록 신초 생장과 발근이 왕성하다. 따라서, 현지외 보전을 위해 향후 휴면성의 종자 발아 연구가 필요하며, 영양번식을 할 경우 근삽이 가장 효율적인 것을 확인하였다.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.246-256
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• 2006

The plane wave reflection coefficient is an acoustic property containing all the information concerning the ocean bottom and can be used as an input parameter to various acoustic propagation models. In this paper, we measure the plane wave reflection coefficient, the sound speed, thd the attenuation for saturated granular medium in the water tank. Three kinds of glass beads and natural sand are used as the granular medium. The reflection experiment is performed with the sinusoidal tone bursts of 100 kHz at incident angles from 28 to 53 degrees, and the sound speed and attenuation experiment are performed also with the same signal. From the measured reflection signal, the reflection coefficient is calculated with the self calibration method and the experimental uncertainties are discussed. The sound speed and the attenuation measurements are used for the estimation of the porosity and permeability, the main Biot parameters. The estimated values are compared to the directly measured values and used as input values to the Biot theory in order to calculate the theoretical reflection coefficient. Finally, the reflection coefficient predicted by Biot theory is compared to the measured reflection coefficient and their characteristics are discussed.

• Journal of the Korean Society of Costume
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• v.50 no.7
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• pp.195-218
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• 2000

This study investigates the characteristics of European knitted works from a historical perspective. Specifically, this study deals with the following research topics: 1) the origin and development of knitting. 2) the characteristics of knitting industry according to the change of times, 3) the comparison of local knitting patterns and cultures. 4) 7he symbolic meaning of the designs in the knitted works and theire functions. This research is barred on the survey of the relevant literature and photographs. The results of the study are summarized as follows. 1) The introduction of knitted works was closely connected with the climatic and socio-economic conditions of the places of the origin. Knitted work developed mostly in Northern Europe, a cold area, and the barren, mountainous coastal areas where people frequently used woolen materials for clothes. 2) In ancient times, abstract and geometric patterns have developed in Europe under the influence of Arabian knitted work. Middle Ages saw the flourishing of Arabian knitted works representing the authority of the church. In early modern times, the knitted work assumed the wealth of the royal families and the nobles. But afterward it was gradually Popularized among the middle classes. Knitting was then regarded as one of the women's major cultural activities. However, recently in the interwar periods. the knitting industry did not flourish and the knitted works came to serve merely as comfort goods by political urge. Knitted works were introduced in Korea around 1870 (the 7th or 8th year of king Kojong era) by Catholic missionaries and they started to be made by machine in 1917. 3) As for the propagation of the knitted work into Europe, there are three routes estimated. The traditional knitting patterns of local areas and their characteristics are summed up as follows : (1) England Guernseys are thick dark blue wool, whereas Jerseys are thinner and of various colors. The knitted shawls of Shetland are world-famous for their fine, lace-like texture that they can be through a wedding-ring. The knitted work of Fair Isle shows several distinctive features, such as the use of no more than two colors, patterns with diagonal lines. symmetry within the patterns, the prominent OXO patterns, and horizontal bands of patterning. The representative knitted work of Aran is Aran sweater made for fishermen to developed from guernseys of Scotland. (2) Scandinavian countries are distinguished from other countries by their conservative but creative cultural tradition. Their knitting patterns are characterized by small geometric figures such as dots, triangles, squares, rhombuses, and crosses used often with stars and roses. Scandinavian knitting is also salient for its vertical stripes and simple motifs repeating at short intervals. (3) Baltic area : The Latvian and Lithuania stockings have very ornate patterns. Many of the Estonian knit stockings and mittens share designs. Komi was well-known for its symmetric diamond pattern. Komi patterns include colored stripes, borders of pattern and all-over designs of complex diagonals. (4) Balkan area : In Yugoslavia, the patterns of roses, leaves and flowers were used for stockings, gloves and leggings. Greek knitting resembled southern Russian knitting, which utilized light colored patterns with dark colors for a background. Turkish patterns are symmetric vertically or horizontally. 4) The traditional knitting patterns net only carried symbolic meanings but also served as means of communication. First of all, patterns had incantatory meanings. Patterns also represented Power or authenticity Patterns were symbolic of one's social standing, too. The colors, motifs and their arrangements were very important features symbolizing one's social position or family line. People often communicated by certain pieces of knitted work or patterns.