• Journal of Communications and Networks
• /
• v.2 no.1
• /
• pp.76-84
• /
• 2000

Communication systems, including cell-based mobile communication systems, multiple satellite communication systems of multi-beam satellite systems, require reliable handoff methods between cell-to-cell, satellite-to-satellite of beam-to-team, respectively. Recent measurement of a CDMA cellular system indicates that the system is in handoff at about 35% to 70% of an average call period. Therefore, system reliability during handoff is one of the major system performance parameters and eventually becomes a factor in the overall system capacity. This paper presents novel and improved techniques for handoff in cellular communications, multi-beam and multi-satellite systems that require handoff during a session. this new handoff system combines the soft handoff mechanism currently implemented in the IS-95 CDMA with code and packet diversity combining techniques and an iterative decoding algorithm (Turbo Coding). the Turbo code introduced by Berrou et all. has been demonstrated its remarkable performance achieving the near Shannon channel capacity [1]. Recently. Turbo codes have been adapted as the coding scheme for the data transmission of the third generation international cellular communication standards : UTRA and CDMA 2000. Our proposed encoder and decoder schemes modified from the original Turbo code is suitable for the code and packet diversity combining techniques. this proposed system provides not only an unprecedented coding gain from the Turbo code and it iterative decoding, but also gain induced by the code and packet diversity combining technique which is similar to the hybrid Type II ARQ. We demonstrate performance improvements in AWGN channel and Rayleigh fading channel with perfect channel state information (CSI) through simulations for at low signal to noise ratio and analysis using exact upper bounding techniques for medium to high signal to noise ratio.

• Journal of Species Research
• /
• v.8 no.1
• /
• pp.136-159
• /
• 2019

This study was carried out to investigate the flora of six islands belonging to the Gogunsan Archipelago (i.e., Sinsi-do, Seonyu-do, Munyeo-do, Yami-do, Bian-do, and Duri-do) in the Korean Peninsula. As results of five field surveys from March to October of 2016, we have identified 575 total taxa, representing 527 species, five subspecies, 42 varieties, and one hybrid, placed in 358 genera and 118 families. Of these 575 taxa, four are endemic to Korea, six taxa are listed on the Korean Red List of threatened species, 67 are floristic regional indicator plants, and 74 are invasive alien species. In this study, we compared species richness among the islands, and find that the larger the islands, the higher the species richness. In the case of habitat affinity types, forest species were most common, followed by farmland, seacoast, bare ground and wetland species. From similarity analyses based on the composition of vascular plants, each island did not exhibit either local specificity or unique diversity. On the contrary, the proportion of invasive alien and ruderal species may increase by human activities. Investigations and analyses of island flora such as this are important to assess the current status of the flora, predict future vegetation patterns and the spread of the alien species, and establish managment plans of plant diversity.

• Journal of agriculture & life science
• /
• v.50 no.1
• /
• pp.1-22
• /
• 2016

In this study, the securing state of nationally indicated beneficial microbial resources was evaluated in an aspect of bio-diversity using their taxonomical information. Depending on the analysis result with the Margalef's richness or the Mehinick's index which are representative bio-diversity analytical indices, species diversity values was revealed as 8.537, 3.546 within bacterial resources, 3.349, 2.167 within fungal resources. Several developed or researched beneficial strains and spoilage microbes showed relative taxonomical relationship with comparation of their biological information. As a result, we propose the necessity or countermeasure method for preventing the microbial spoilage with the overhauling consideration of advanced research on agricultural microbiology covering crop endophyte beneficial/spoilage microorganisms.

• Journal of Satellite, Information and Communications
• /
• v.2 no.2
• /
• pp.1-9
• /
• 2007

In this paper, we describe the performance degradation of satellite Wibro system and compensation method in the high-speed railroad channel environment. High-speed railroad channel environment is divided into LOS channel and tunnel. In the LOS channel, signal blocking caused by railroad power feeder structures can be a critical problem which is can be solved with antenna diversity. On the other hand, multi path interference phenomenon, representable by propagation model of Optic Fiber, occurred in the tunnel may be another obstacle. These satellite Wibro system performance degradations in railroad channel environment are addressed and adequate compensation methods are proposed and verified through computer simulation. In addition, the ICI caused by Doppler shift in OFDM system is analyzed with its compensation method.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.7
• /
• pp.858-866
• /
• 2019

In line with the transformation of the shipping industry, the number of mixed-manning ships is on the rise - bringing foreign sailors aboard with their local sailors. During on-board work, a culture is formed according to mixed-manning, which leads to changes in on-board living environment. This causes various problems such as communication problems, and lack of education and training. In order to identify and solve problems caused by mixed-manning, this study presented a plan for systematic education of foreign seafarers. The officials in charge of the affairs of foreign sailors conducted questionnaire surveys at various shipping lines. The questionnaire survey results were analyzed using the IBM SPSS Statistic 26 program. Three improvement measures were proposed to solve the problems after identification of the types of education, education methods, and problems of foreign employees. This study revealed that it is imperative to systematize related education of foreign seafarers based on the results of the survey.

• Journal of Ecology and Environment
• /
• v.45 no.4
• /
• pp.237-254
• /
• 2021

Background: Some of the introduced alien species introduced settle, multiply, and spread to become invasive alien species (IAS) that threaten biodiversity. To prevent this, Korea and other countries legally designate and manage alien species that pose a risk to the environment. Moreover, 2160 alien species have been introduced in South Korea, of which 1826 animals and 334 plants are designated. The inflow of IAS can have negative effects such as ecosystem disturbance, habitat destruction, economic damage, and health damage to humans. To prevent damage caused by the inflow of IAS in advance, species that could potentially pose a risk to the environment if introduced in South Korea were designated as alert alien species (AAS). Results: The designation criteria were in accordance with the "Act on the Conservation and Use of Biological Diversity" and the "Regulations on the Ecological Risk Assessment of AAS and IAS" by the National Institute of Ecology. The analysis result of risk and damage cases indicated that mammals affect predation, competition, human economic activity, virus infection, and parasite infection. Birds have been demonstrated to affect predation, competition, human economic activity, and health. It was indicated that plants intrude on the ecosystem by competing with native species with their high-population density and capacity to multiply and cause allergic inducement. Interestingly, 300 species, including 25 mammals, 7 birds, 84 fishes, 28 amphibians, 22 reptiles, 1 insect, 32 spiders, 1 mollusk, 1 arthropod, and 99 plants, are included in the list of AAS. Conclusions: AAS designation plays a role in preventing the reduction of biodiversity by IAS in South Korea and preserving native species. Moreover, it is determined to provide considerable economic benefits by preventing socio-economic losses and ecological damage.

• Korean Journal of Environment and Ecology
• /
• v.28 no.3
• /
• pp.293-301
• /
• 2014

15 artificial ponds in Seoul have been examined to find out the characteristics of Odonata community according to age and size of pond. We found 6 Families 36 Species of Odonata community, and Libellulidae was the most frequent and 19 Species were observed among Libellulidae. Considering relative importance with frequency of appearance and density, Ischnura asiatica and Orthetrum albistylum was the most frequent. Also, 16 Species including Lestes temporaris, Sympetrum parvulum, and Anax nigrofasciatus were relatively rare. The result of dominant species tells that Ischnura asiatica in 1 ~ 3 year old ponds, Pantala flavescens-Orthetrum albistylum-Crocothemis servilia mariannae in order of mention in 4 ~ 6 year old ponds, Platycnemis phyllopoda-Ischnura asiatica in order of mention in 10 or more year old ponds are the dominant species. Species diversity index regarding age of pond has been researched, and species diversity index in 10 year old pond was higher than that of in 1 ~ 3 year old pond. Having done the analysis of variance for types of spawn, there are many species Endophytic egg-layers and pasting in mud or sand in 10 year old artificial ponds. The wider ponds get, the higher species diversity index gets. And, we suggest that desirable size for making artificial ponds to increase the species diversity index of Odonata is $100{\sim}300m^2$.

• Korean Journal of Food Science and Technology
• /
• v.31 no.6
• /
• pp.1619-1627
• /
• 1999

Microbiological characteristics of gamma irradiated low salt squid Jeot-gal were examined. Following the fermentation periods, total bacterial cell, Lactobacillus spp., Staphylococcus spp., Streptococcus spp., Pseudomonas spp. and yeast cell number were counted on their selective media and some acid forming bacteria and Pseudomonas spp. were identified. As the gamma irradiation dose increased, the microbial density of early fermentation phase was reduced and the growth rate was delayed. The repression effects on microbiological growth by gamma irradiation were to be higher as salt concentration increased. Adequate conditions of salt concentration and gamma irradiation for low-salt squid Jeot-gal preparation were 10% and 10 kGy, respectively. Lactobacillus sp. 2, Micrococcus varians and Streptococcus sp. I were isolated from 5% salt containing squid Jeot-gal, and Micrococcus morrhuae was from 20% only while Lactobacillus plantarum and Lactobacillus brevis were widespread. Lactobacillus brevis, Pediococcus halophilus and Pseudomonas diminuta were sensitive and Lactobacillus plantarum, Micrococcus morrhuae and Pseudomonas sp. 3 were resistant to gamma irradiation. The diversity of microflora decreased as salt concentration decreased and gamma irradiation dose increased.

• Korean Journal of Environment and Ecology
• /
• v.36 no.3
• /
• pp.220-256
• /
• 2022

The most important thing for conserving plant diversity in an area is to make an overall inventory of the plant species inhabiting the area. In particular, limestone areas are known for their high plant diversity and distribution of specific plants. Despite that, only a few have been designated as protected areas. This study investigated the vascular plants distributed in Goyangsan Mtn. and Munraesan Mtn., located in limestone areas of the central part of the Korean Peninsula. A field survey was conducted eight times from April to October 2021. As a result, we identified a total of 654 taxa comprising 113 families, 357 genera, 592 species, 15 subspecies, 44 varieties, and 3 formulas. They included four endangered wild plant species: Astilboides tabularis, Eleutherococcus senticosus, Cypripedium macranthos, and Epilobium hirsutum. Endemic plants in Korea were identified as 32 taxa. Floristic target plants were identified as 168 taxa, specifically 5 taxa of grade V, 41 taxa of grade IV, and 36 taxa of grade III. The red data plants included 2 taxa as "Endangered (EN)", 7 taxa as "Vulnerable (VU)", and 7 taxa as "Near threatened (NT)". A total of 41 taxa of naturalized plants were identified, and 4 of them were invasive alien plants. The surveyed vicinity of Goyangsan Mtn. and Munraesan Mtn. showed high plant diversity and contained core habitats for distribution of an endangered wild plant, Astilboides tabularis,in the limestone area. Moreover, both mountains contained a small population of Cotoneaster integerrimus. These findings confirm that the area has conservation values. Therefore, we propose to identify areas with high plant diversity and designate them as special protected areas.

• Animal Systematics, Evolution and Diversity
• /
• v.12 no.3
• /
• pp.221-235
• /
• 1996

The ascidians of Chundo Island are identified into 15 species, 8 genera, 6 families. Among them two species are found to be new to Korean fauna. They are Ascidia sydneiensis Stimpson and Ascidia zara Oka. They are described with figures, and the other species are provided with remarks.