• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.03a
• /
• pp.75-85
• /
• 2006

In recent geotechnical engineering, geothermal approach has been on the horizon to deal with geoenvironmental issues, freezing and thawing problems, and seepage phenomenon in dams and embankments. In this study, geothermal characteristic through inner body of dams and its influence on the seepage flow were experimented by lab test and field instrumentation. Also, one of up-to-date temperature monitoring technique, called as multi-channel thermal line sensing, was evaluated its availability. As a result of lab test, it is found that the seepage flow has influence on the geothermal characteristic and a potential of finding phreatic line and seepage fluctuation could be possible by continuous temperature monitoring using thermal line sensing skills. These kine of geothermal information could be available to the modelling of water geo-structure interaction. Out of short-term field tests, clear water table and temperature distribution of a dam were easily found through temperature monitoring in holes located near a reservoir and holes within a depth of constant temperature layer. However, it is also found that the geothermal flow and finding seepage line could not be easily understandable through multi-channel temperature monitoring because of the existence of constant temperature field, thermal conductivity of soils and rocks, and unsaturated characteristics of geo-material. In this case, long-term geothermal monitoring is recommended to find sudden fluctuation of seepage line and amount of leakage.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.376-383
• /
• 2005

In this study, we conducted geophysical investigations for the organization of integrated geophysical methods to detect underground cavities of ground subsidence area at the field test site, located at Yongweol-ri, Muan-gun. We examined the applicability of geophysical methods such as electrical resistivity, electromagnetic, and microgravity to cavity detection with the aid of borehole survey results. Underground cavities are widely present within the limestone bedrock overlain by the alluvial deposits in the area of the test site where the ground subsidences have occurred in the past. The limestone cavities are mostly filled with groundwater and clays in the test site. Thus, cavities have low electrical resistivity and density compared to the surrounding host bedrock. The results of the study have shown that the zones of low resistivity and density correspond to the zones of the cavities identified in the boreholes at the site, and that the geophysical methods used are very effective to detect underground cavities. Furthermore, we could map the distribution of cavities more precisely with the test results incorporated from the various geophysical methods. It is also important to notice that the microgravity method is a very promising tool since it has rarely used for the cavity detection in korea. Beyond the investigation of underground cavities, the geophysical methods are required to provide useful information for the reinforcement design for the ground subsidence areas. It is, therefore, necessary to develop integrated geophysical technique incorporating different geophysical methods to precisely map underground cavities and image the subsurface of the ground subsidence areas.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.7
• /
• pp.128-134
• /
• 2010

In this paper, a high-power 20-way stripline power divider with low insertion loss and low side lobe level is successfully designed, fabricated and measured as a feed network for an S-band linear array antenna having Dolph-Chebyshev current distribution which has a narrow beam width and very low side lobe level (SLL). The 20-way stripline power divider consists of an 8-way power divider, three 4-way power dividers and three ring hybrids. It utilizes a T-junction structure as a basic element for power dividing. Notches and modified input/output N-to-stripline transitions are used for improving insertion loss and return loss. The fabricated power divider shows insertion loss less than 0.3 ㏈ and rms phase mismatch less than 8o in the full bandwidth. A final 40-way power divider is synthesized by combining symmetrically two 20-way power dividers and is expected to have SLL over 40 dB, based on the measured results of the 20-way power divider.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.48 no.6
• /
• pp.71-80
• /
• 2011

According to rapid development of communication and video compression technology, the video contents are easily disseminated into various areas. In order to prevent illegal distribution of video contents, the necessity of video contents protection technology is increased. In this paper, we propose the video encryption and decryption algorithm based on logistic map and design the prototype system in real-time embedded environment. The sender system with encryption capability is implemented on DM642 EVM target board and the receiver system with decryption capability is implemented in satellite D-STB. Experimental results show that the time change ratio of encoding process on target board are less than 0.97% and the time change ratio of the decoding process on D-STB is less than 1.75%. So, we verify that the proposed encryption/decryption system can be used in real time application.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.48 no.3
• /
• pp.12-17
• /
• 2011

In this paper, we report on the improved electrical and optical characteristics for decreasing current crowding effect and uniform current distribution by designing octagonal finger type electrode pattern in large-scale lateral GaN (Gallium Nitride) LED (Light-emitting diode) with numerical 3-D simulator. Compared with the conventional electrode pattern, proposed electrode pattern was investigated to confirm the improvement of characteristics. From the simulation results of 3-D SpeCLED/RATRO simulator, we found that the forward voltage was decreased by 0.34 V and the light output power was improved by 7.72 mW at the same injection current condition in the LED with proposed octagonal finger type electrode.

• Journal of Forest and Environmental Science
• /
• v.31 no.3
• /
• pp.192-201
• /
• 2015

Information on plant diversity and community structure are required to chalk out necessary actions for conservation management. The present study assessed the composition and diversity of tree species in Kamalachari Natural Forest of Chittagong South Forest Division, Bangladesh, during April 2010 to November 2011. A total of 107 tree species belonging to 72 genera and 37 families were recorded, where Moraceae family was represented by maximum (11) species. Density, Basal area and volume of tree species were $418{\pm}20.09stem/ha$, $21.10{\pm}2.62m^2/ha$ and $417.4{\pm}79.8m^3/ha$ respectively. Diameter and height class distribution of tree species revealed an almost reverse J-shaped curve. Both the number of species and percentage of tree individuals were maximum in the lower DBH and height ranges. Anthropogenic disturbances like illegal tree cutting, over extraction, settlement inside forest area etc. were noticed during the study, which are supposed to cause gradual decrease of both tree species and individuals in the higher DBH and height classes. However, Artocarpus chama was found dominant showing maximum IVI followed by Schima wallichii, Aporosa wallichii, and Lithocarpus acuminata. The quantitative structure of the tree species of Kamalachari natural forest is comparable to other tree species rich tropical natural forests. The findings of the study may help in monitoring future plant population changes of the identified species and adopting species specific conservation programs in Kamalachari natural forest.

• Korean Journal of Ichthyology
• /
• v.21 no.sup1
• /
• pp.74-74
• /
• 2009

The perciform suborder Labroidei comprising six families (Cichlidae, Embiotocidae, Pomacentridae, Labridae, Odacidae, and Scaridae) are characterized by having the specialized pharyngeal jaws for food processing, i.e., united fifth ceratobranchials and upper pharyngeal jaw articulating with the basicranium via diarthroses (Stiassny and Jensen, 1987). They usually inhabit in the most tropical and subtropical seas and comprise about 235 genera and roughly 2,274 species worldwide (Nelson, 2006). Concerning the Korean labroid fishes, Mori (1952) had listed 18 genera and 26 species belong to four families in his check list of Korean fishes since Jordan and Metz (1913) firstly reported six genera and seven species in only two families (Embiotocidae and Labridae). Chyung (1977) added two species, Tilapia mossambica and Cirrhilabrus temmincki, to Mori’s list and also classified them into three suborders, i.e., Embiotocina (containing only Embiotocidae), Pomacentrina (Cichlidae and Pomacentridae), and Labrina (Labridae and Scaridae). Subsequently, Lee and Kim (1996) reviewed the Korean labroidfishes taxonomically resulting in 22 genera and 32 species in five families with some taxonomical modifications including a new Korean record. It is remarkable to be added many new Korean recordsto the pomacentrids or the labrids for recent 10 years (Koh et al., 1995; Yoo et al., 1995; Koh et al., 1997; Myoung, 1997; Choi and Kim, 2000; Choi et al., 2002; Kim and Go, 2003). Recently, Kim et al. (2005) briefly described all members of the Korean Labroidei with a color photograph or a figure, recognizing 27 genera and 42 species in five families. In the present study, the current taxonomical status of the Korean labroid fishes including distributional features is summarized based both on specimens collected from the Korean waters and on literature survey to provide bio-information of the Korean native fish species. As a result, the Korean labroid fishes totally consist of 27 genera and 44 species in five families, that is, Cichlidae (1 species), Embiotocidae (3), Pomacentridae (15), Labridae (22), and Scaridae (2). They distributed mainly in the coastal waters of the South Sea, Korea, however, most pomacentrids or labrids occur in the coastal waters of Jeju Island only, although some species were observed in their larval or juvenile stages only from coastal waters of the island. Interestingly, several species are expanding their distribution north to Ulreung and Dok islands in the East Sea, Korea lately.

• Journal of Ecology and Environment
• /
• v.38 no.3
• /
• pp.353-360
• /
• 2015

A survey of weed occurrence was conducted to identify problematic weed species in a horticultural crop field to get basic information for effective weed control. Surveys of weed species occurring in horticultural crop fields (garlic, onion, red pepper and Chinese cabbage) were conducted in Chungnam province of Korea from April to October in 2014. A total of 516 sites of the 17 regions were identified as having 114 weed species belonging to 32 families. The most dominant weed species in the horticultural crop fields were Chenopodium album var. centrorubrum (8.83%), followed by Digitaria ciliaris (5.71%), Conyza canadensis (5.46%) and Capsella bursa-pastoris (4.67%). Specifically, as a result of this study, the occurrence of 35 species of exotic weeds, such as Chenopodium album and Taraxacum officinale, were confirmed. Almost 68% of the investigation sites was determined under dominance value 1 (range of cover < 10; numerous individuals) by Braun-Branquet cover-abundance scale, indicating a proper weed control in horticultural crop field. As a result of scientific and technological advances, an improved cultivation method is changing the weed occurrence in agricultural land. Additional research needs to be undertaken for the development of weed control methods through such periodic monitoring of occurrence of weeds.

• Journal of Environmental Science International
• /
• v.20 no.12
• /
• pp.1521-1531
• /
• 2011

This study was carried out to determine the characteristics of the marine environment, including nutritional content, in order to clearly understand the outbreaks of Gonyaulax polygramma in the southern coastal areas in August, 2009. Samples were collected at 13 sites and water temperature and salinity were measured using a CTD. Field surveys were twice: the first between August 5-7, the second between August 22-24. The cell density of G. polygramma was 6,500-10,000 cells $ml^{-1}$ during the $1^{st}$ survey, whereas during the $2^{nd}$ survey the range of the cells was recorded from 8,000 to 12,500 cells $ml^{-1}$. Cochlodinium polykrikoides ranged from 0 to 105 cells $l^{-1}$ during the field survey. In water environments, the majority stations during the $1^{st}$ survey showed a nearly homogeneous water column below $1^{\circ}C$ in temperature, as well as similar profiles of salinity. However, the stratification between the surface and bottom was observed in the $2^{nd}$ survey. Regarding nutrients, Dissolved Inorganic Nitrogen (DIN) in the surface ranged from 0.144 to 0.236 mg $l^{-1}$ during the $1^{st}$ survey, and 0.082-0.228 mg $l^{-1}$ during the $2^{nd}$ survey. DIP (Dissolved Inorganic Phosphorus) did not show any difference in concentration between the $1^{st}$ and $2^{nd}$ survey. During August of 2009, the wind speed in the southern waters remained at around ${\leq}2\;m\;s^{-1}$ for about 60% of time, and there was very little precipitation during the month. Irradiance of ${\geq}10$ hr was shown in the late of August. It is thought that a low level of DIN and salinity play an important role as an essential factor for rapid growth, wide distribution and longer duration of red tide in G. polygramma.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.22 no.4
• /
• pp.92-100
• /
• 1985

New N+N/P HLE solar cells with N+ surface charge accumulated layer in the emitter region are fabricated on the N/P Si epiwafer by incorporating high fixed positive charge density (Qss) at the Si-AR layer interface. Solar cells are classified into two categories, i.e, OCI and NCI Cell depending on AR layer, SiOl and Si3 N4/sioxynitride layer respectively. The distribution of Qss in the Si-AR layer interface is examined by C-V plot. It shows that the surface charge accumulated layer is formed more effectively in the NCI cell (Qss=1.79-1.84$\times$1012cm-2) than in the OCI cell (Qss=3.03~4.40$\times$1011 cm-2). The efficiency characteristics are evaluated under the JCR halogen lamp of 100 mw/cm2. The average (maximum) conversion efficiency for active area is 15.18 (15.46)% in the OCI cell and 16.31 (17.07)% in the NCI cell.