• Title/Summary/Keyword: core density

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A Study on the Atomizing Mechanism for the Swirl Nozzle (와권(渦卷) 노즐의 무화기구(霧化機構)에 관(關)한 연구(硏究))

  • Lee, Sang Woo;Sakai, Jun;Ishihara, Akira
    • Korean Journal of Agricultural Science
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    • v.14 no.1
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    • pp.81-97
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    • 1987
  • Two nozzles with different size (Figure 2) were particularly designed to supply air through the swirl core into the central part of the liquid stream in the same parallel direction to produce a well-mixed air and water in the whirl chamber as spray liquid in bubble formation. Atomization was attempted to improve by using both the preliminary break-up process with less viscosity and less surface tension in the whirl chamber and the effects of increased frequency of the band of drops with the raised ambient air density in front of the nozzle orifice. The volumetric ratio between spray liquid and air on four levels was used to investigate the effects of air as a component of the mixture on atomization. The results of the experiment were summarized as follows; Droplet size became progressively finer as the operating pressure was increased in the range of $0.70kg/cm^2$ to $6.33kg/cm^2$, which was similar to the previous works. The new atomizing mechanism so-called 'air-center nozzle' gave a narrower range in droplet size distribution with smaller volumetric median diameter (VMD) than that of the existing spray system at a given pressure, which showed the possibility of improvement of atomization in a certain limit. The volumetric median diameter produced by the new atomizing mechanism was decreased from the central region toward the exterior edges across the spray pattern.

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Integrated Interpretation of ERT Data from the Mineralized Zone in Geumpung Mine (금풍광산 광화대에 대한 전기비저항 토모그래피탐사 자료의 복합해석)

  • Jung, Yeon-Ho;Byun, Joong-Moo
    • Geophysics and Geophysical Exploration
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    • v.10 no.4
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    • pp.322-331
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    • 2007
  • In this study, electrical resistivity tomography (ERT) were conducted to find the mineralized zone at the Geumpung mine in Dojeon-ri, Susan-myeon, Jecheon-si, Chungcheongbuk-do. The deviation of the inclined borehole was measured to obtain the exact positions of the electrodes for correcting apparent resistivity values from ERT. Geophysical loggings such as resistivity and natural gamma were conducted to obtain the properties of the material near the borehole. Measurements of the physical properties of the cores, such as porosity, water content, density, susceptibility, resistivity were performed to analyze the correlation between physical properties and resistivity. Grade analysis for core sample was also conducted to identify relationship between grade and resistivity. Rock property analysis shows that the resistivity is more dominated by susceptibility and grade than by porosity and water content in the mineralized zone. The results of ERT are well consistent with geophysical logging data and geologic column. So ERT is powerful method to identify conductive mineralized zone.

Interpretation of Subsurface Fracture Characteristics by Fracture Mapping and Geophysical Loggings (단열조사 및 물리검층을 통한 지표 하 단열특성 해석)

  • Chae, Byung-Gon;Lee, Dae-Ha;Kim, Yu-Sung;Hwang, Se-Ho;Kee, Weon-Seo;Kim, Won-Young;Lee, Seung-Gu
    • Journal of the Korean GEO-environmental Society
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    • v.2 no.1
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    • pp.37-56
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    • 2001
  • As a preliminary study to establish fracture network model in crystalline rocks, detail investigation on fracture characteristics were performed. Five fracture sets were determined on the basis of regional survey of geological structures and fractures on outcrops. Among the fracture sets, S1 set has the highest density and longest trace length of fractures which was identified on surface in the study area. S4 and S5 sets are composed of foliations and foliation parallel shear joints of gneisses, which are very important sets at the aspect of weighting of fracture length. For characterization of subsurface fractures, detail core logging was performed to identify fractures and fracture zones from five boreholes. Acoustic televiewer logging and borehole geophysical loggings produced images, orientations and geophysical properties of fractures which intersect with boreholes. According to the result of the investigations, subsurface fractures can be grouped as three preferred orientations(B1, B2 and B3), which correspond to S1, S2 and S4/S5 of surface fracture sets, respectively. Actually, B1 set is expected to be intensely developed at subsurface. However, it has low frequency of intersection with boreholes due to its parallel or sub-parallel direction to boreholes. According to the inference of conductive fractures, B1 and B3 sets have possibilities of water flow and their intersection lines are also thought to consist of important conduits of groundwater flow. In particular, faults which are parallel to foliations control major groundwater flow in the study area.

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A geographical study of the Korean Tobacoo forming region (韓國 煙草載培地域의 地理學的 硏究)

  • ;Kim, Kwang Ja
    • Journal of the Korean Geographical Society
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    • v.21
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    • pp.16-37
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    • 1980
  • The purpose of this study is to clarify how the Korean tobacco farming region has been geographically formed by natural and cultural environments, and to examine and cultural environments, and to examine whether it can be recognized as a major part of agricultultural regions. The questions asked in this study are associated with the spatial diffusion of tobacco cultivation, the patterns and processes of the farming region from 1900 to 1960, and the regional characteristics of the concentrated farming area since 1960. The study is inductively approached and most data used were collected from old records and field works. The delineation of the tobacco farming region was derived by applying the concept of the uniform region. Tobacco was introduced through Japan during the years of Kwang Hae Kun (1616-1622). According to the old records, three places, Waekwan, Dongrae, and Ulsan, were the first tobacco raising areas. In the 1700's the well-known tobacco farming regions were scattered all around the nation in places like Jinan, Samdeung, Seongcheon, Gangdong, Yeongweol and Yeongyang. This distributon pattern suggests that tobacco farming in Korea developed spatially along main traffic routes before the 1700's. Untill the 1920's the pattern of tobacco regions was relatively static. Since the 1920's, it has shown a pattern of concentration in the Choongbuk province, where the new highly productive yellow tobacco has been introduced. It was not until the 1960's that yellow tobacco instead of the native variety came to be cultivated all over the country. In the 1960's, the tobacco farming region tended to be concentrated and localized in north western Choongnam, northern Cheonbuk, Choongbuk, and Kyeongbuk including Cheongsong, Andong, and Yeongyang. Since 1970, tobacco production has declined in some of the former major areas of cultivation in terms of its density, while there have appeared highly concentrated areas in Cheongsong and Andong, centered around Yeongyand. There has also emerged a secondary major concentrated area along the coast including such places as Kochang, Yeongkwang and Mooan. The appearance of the Yeongyang tobacco area as the most important core region can be described as follows; at first this area has the disadvantage of being in competition with other places for selling cash crops besides tobacco, because it is located in a mountain zone and it is far from the major metropolises of Seoul and Pusan. Thus has been formed the farming mentality that agricultural management makes the most profit on farming tobacco because tobacco is stable in price and selling routes. As a result of this longstanding belief, these areas (Yeongyang, Cheongsong and Andong) have developed into tobacco concentrated regions. Finally, the tobacco concentrated regions of Korea have changed through time. The factors affecting this change have been the kind of tobacco grown, the monopoly system, agricultural techniques and the expansion of arable land through the clearing of slopes. In conclusion, the research indicates that the localized and concentrated patterns of tobacco cultivation are geographically typical. Thus, recognition of tobacco farming region is important to understanding the agricultural region of Korea as a whole.

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Steady-state Thermal Analysis of 5 kW IPMSM Using Thermal Equivalent Circuit (열등가회로를 이용한 5 kW 급 영구자석 동기전동기의 정상상태 열 특성 해석)

  • Kim, Tae Hyun;Yoo, Young Bum;Na, Jong Seung;Ryu, Kyongtae;Moon, Yoon Jae;Lee, Jae Heon;Lee, Ju;Park, Chan Bae;Moon, Seung Jae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.11
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    • pp.951-956
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    • 2014
  • Steady-state thermal analysis was performed on a thermal equivalent circuit to determine the heat generation during operation of an interior permanent magnet synchronous motor (IPMSM). New machines must be compact and light and produce high torque density under extreme environmental conditions. Thermal analysis of an IPMSM is particularly important because excessive heat generated from the core and magnet reduces the IPMSM's output and has adverse effects on the durability. Therefore, steady-state thermal analysis of an IPMSM was performed for changes in the design variables using a thermal equivalent circuit. The changed variables were the axis length and thickness of the housing. The results of this method were compared with those of the finite element method to verify the accuracy and reliability.

Analysis of Macrobenthic Community Structure in an Intertidal Flat in Hakseong-ri, Boryeong, Korea (보령 학성리 갯벌 조간대 대형저서동물 군집구조 분석)

  • YANG, DONGWOO;LEE, JUNG-HO;KIM, HARYUN;BAE, HANNA;PARK, JINSOON;KIM, HYE SEON
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.26 no.3
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    • pp.167-182
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    • 2021
  • This study was carried out to investigate temporal and spatial distribution of macrobenthic community and elucidate effects of environmental factors on change of community structure in an intertidal flat, Hakseong-ri, Boryeong, Korea. Field surveys were seasonally conducted to collect samples of sediment and macrobenthos using can core in triplicate at nine stations in 2016 and 2017. Our results showed that sediment had high mud content (above 60%) in most samples and mean content of loss on ignition was 2.3% in 2016. A total of 79 species was collected in the study site during the study period. Mean density and biomass were 611 ind./m2 and 64.1 gWWt/m2, respectively. Heteromastus filiformis was the dominant species (48.6%, 297 ind./m2) followed by Macrophthalmus japonicus (10.1%, 62 ind./m2) and Upogebia major (6.9%, 42 ind./m2). Three assembly groups resulted from cluster analysis were more distinguished by interaction between organisms and frequency of dominant species than by physical and chemical environment characteristics. In addition, macrobenthic community in the Hakseong intertidal flat showed seasonal changes based on non metric multidimensional scaling using species abundance.

Effect of Moulding Conditions on Properties of Table Top for Student Desk Manufactured by Wood Waste Materials (폐기 목질 재료로 제조한 학생용 책상 천판의 성능에 미치는 성형조건의 영향)

  • Roh, Jeang-Kwan;Kim, Jae-Kyung;Kim, Sa-Ick;Jo, Jong-Soo;Yoon, Seung-Lak;Ra, Jong-Bum;Do, Jeong-Lak
    • Journal of the Korean Wood Science and Technology
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    • v.30 no.4
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    • pp.106-113
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    • 2002
  • This research was performed to investigate the effect of moulding conditions on properties of the table top for student desk manufactured by wood waste materials. The table top manufactured using the mat mixed properly with fine particles and coarse particles generally showed better physical properties than those manufactured using either fine particles or coarse particles did/ Especially, highest performance for overlaying was observed when fine particles were used for face layer and coarse particles were used for core layer. The internal bond (IB) strength, the bending strength and thickness swelling increased with the increase of density. Most of physical properties were improved with the increase of hot pressing temperature. The best physical properties were found at 190℃ when the first hot pressing and the second hot pressing times were two minutes. However, the effect of the second hot pressing time of two minutes on the physical properties was not markedly different from that of one minute. This result suggests that the second hot pressing time of one minute is enough to increase the productivity in manufacturing the table top with the least decrease of the physical properties.

Case study of information curriculum for upper-grade students of elementary school (초등학교 고학년 정보 교육과정 사례 연구)

  • Kang, Seol-Joo;Park, Phanwoo;Kim, Wooyeol;Bae, Youngkwon
    • Journal of The Korean Association of Information Education
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    • v.26 no.4
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    • pp.229-238
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    • 2022
  • At the time of discussing the 2022 revised curriculum, the demand for normalization of information education is increasing. This study was conducted on the case of the information curriculum for the upper elementary grades responding to such needs. For 14 6th grade students of Elementary School B in K Metropolitan City, 4 core areas of the information curriculum, including computing system, data, algorithm & programming, and digital culture, were covered through classes. Cooperative classes were conducted between students by using the cloud-based application according to the class. In addition, it was intended to supplement the curriculum by suggesting ideas for artificial intelligence education area, and to improve the density of research with additional investigation on foreign information education cases. However, the need for independent organization of the information curriculum was strongly confirmed in that the current curriculum for information classes lacked sufficient school hours and had to be operated in combination with other subjects in the form of a project for this case study. It is hoped that this study will serve as a small foundation for the establishment of the information curriculum for the upper elementary grades in the future.

Evaluation of bonding state of shotcrete lining using nondestructive testing methods - experimental analysis (비파괴 시험 기법을 이용한 숏크리트 배면 접착상태 평가에 관한 실험적 연구)

  • Song, Ki-Il;Cho, Gye-Chun;Chang, Seok-Bue;Hong, Eun-Soo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.1
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    • pp.71-83
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    • 2009
  • Shotcrete is an important primary support for tunnelling in rock. The quality control of shotcrete is a core issue in the safe construction and maintenance of tunnels. Although shotcrete may be applied well initially onto excavated rock surfaces, it is affected by blasting, rock deformation and shrinkage and can debond from the excavated surface, causing problems such as corrosion, buckling, fracturing and the creation of internal voids. This study suggests an effective non-destructive evaluation method of the tunnel shotcrete bonding state applied onto hard rocks using the impact-echo (IE) method and ground penetration radar (GPR). To verify previous numerical simulation results, experimental study carried out. Generally, the bonding state of shotcrete can be classified into void, debonded, and fully bonded. In the laboratory, three different bonding conditions were modeled. The signals obtained from the experimental IE tests were analyzed at the time domain, frequency domain, and time-frequency domain (i.e., the Short- Time Fourier transform). For all cases in the analyses, the experimental test results were in good agreement with the previous numerical simulation results, verifying this approach. Both the numerical and experimental results suggest that the bonding state of shotcrete can be evaluated through changes in the resonance frequency and geometric damping ratio in a frequency domain analysis, and through changes in the contour shape and correlation coefficient in a time-frequency analysis: as the bonding state worsens in hard rock condition, the autospectral density increases, the geometric damping ratio decreases, and the contour shape in the time-frequency domain has a long tail parallel to the time axis. The correlation coefficient can be effectively applied for a quantitative evaluation of bonding state of tunnel shotcrete. Finally, the bonding state of shotcrete can be successfully evaluated based on the process suggested in this study.

High-Frequency Bottom Loss Measured at Near-Normal Incidence Grazing Angle in Jinhae Bay (진해만에서 측정된 높은 수평입사각에서의 고주파 해저면 반사손실)

  • La, Hyoung-Sul;Park, Chi-Hyung;Cho, Sung-Ho;Choi, Jee-Woong;Na, Jung-Yul;Yoon, Kwan-Seob;Park, Kyung-ju;Park, Joung-Soo
    • The Journal of the Acoustical Society of Korea
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    • v.29 no.4
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    • pp.223-228
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    • 2010
  • High-frequency bottom loss measurements for grazing angle of $82^{\circ}$ in frequency range 17-40 kHz were made in Jinhae bay in the southern part of Korea. Observations of bottom loss showed the strong variation as a function of frequency, which were compared to the predicted values using two-layered sediment reflection model. The geoacoustic parameters including sound speed, density and attenuation coefficient for the second sediment layer were predicted from the empirical relations with the mean grain size obtained from sediment core analysis. The geoacoustic parameters for the surficial sediment layer were inverted using Monte Carlo inversion algorithm. A sensitivity study for the geoacoustic parameters showed that the thickness of surficial sediment layer was most sensitive to the variation of the bottom loss.