• Journal of the Korean Operations Research and Management Science Society
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• v.31 no.3
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• pp.1-10
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• 2006

In this paper we deal with a cell planning issue arisen in a CDMA based multicast network. In a CDMA based wireless network, a terminal can significantly reduce the bit error rate via the cohesion of data streams from multiple base stations. In this case, multiple base stations have to be operated according to a common time line. The cells whose base stations are operated as such are called soft-combined cells. Therefore, a terminal can take advantage of error rate reduction, if the terminal is in a soft-combined cell and at least one neighboring cell is also soft-combined. However, as soft-combining operation gives heavy burden to the network controller, the limited number of cells can be soft-combined. Our problem us to find a limited number of soft-combined cells such that the benefit of the soft-combining operation is maximized.

• Parasites, Hosts and Diseases
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• v.25 no.1
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• pp.59-68
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• 1987

An epidemiological survey on Metagonimus yokogawai infection was performed in the eastern coast area of Kangwon province. Formalin-ether concentration technique and Stoll's dilution egg counting method were employed to figure out the prevalence and intensity of M. yokogawai infection and eating habits of inhabitants with raw freshwater fish. The results are summarized as follows: 1. The prevalence rate of M. yokogawai infection was 6.6% among a total of 2, 357 examinees; 8.6% (115 out of 1, 345) in male and 4.0% (40 out of 1, 012) in female. 2. The prevalence rates were different by the streams where the examinees were residing: 17.8% along the area of Ohsip-cheon (stream), 11.8% along Maeup-cheon, 1.7% along Hwasang-cheon, 1.3% along Yeongok-cheon, 0.9% along Namdae-cheon, 0.9% along Sa-cheon and 0% in the other streams (Yongchon-cheon, Kangnung Namdae-cheon and Jusoo.cheon) in decreasing order. 3. By social strata, the positive rate was 8.0% (122 out of 1, 521) in general inhabitants and 3.9% (33 out of 836) in school children. 4. By the intensity of infection by means of EPG counts in feces; the light infection (less than 400/EPG) was 74.1%, moderate infection (401-1, 000/EPG) 17.3% and heavy infection (more than 1, 001/EPG) 8.6%. 5. Twelves out of 50 sweetfish (Plecoglossus altivelis) (24%) caught from the streams in eastern coast of Kangwon-Do were infected with metacercariae of M. yokogawai, and the number of larvae detected were 70.7 per 6sh in average. The metacercarial infection rates in fish were also different by the streams; 100% in Ohsip-cheon of Samcheok-Gun, 14.3% in Sa-cheon, 16.7% in Yeongokcheon of Myeongju-Gun and 0% in Namdae-cheon of Yangyang-Gun, respectively. 6. Six hundred ninety live (695) out of 1, 396 inhabitants and school children (49.8%) were experienced in eating raw freshwater fishes (Plecoglossus altivezis, Triboledon hakonensis, Coreoperca sp., Morose sp., Carassius sp. & Cyprinus sp. and Zacco platypus). The data were assayed with the questionnaire collected from the examinees. In summarizing the above results, it is known that the Ohsip-cheon area of Samcheok-Gun is highly infected region, and the other areas of Kangnung Namdae-cheon, Yeongok-cheon and Yangyang Namdae-cheon are very lowly infected or non-infected regions for M yokogawai infection.

• Journal of Communications and Networks
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• v.12 no.3
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• pp.222-230
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• 2010

In this paper, we present a closed-form approximation of the average sum rate of zero-forcing (ZF) beamforming (BF) with semi-orthogonal user selection (SUS). We first derive the survival probability associated with the SUS that absolute square of the channel correlation between two users is less than the orthogonalization level threshold (OLT).With this result, each distribution for the number of surviving users at each iteration of the SUS and the number of streams for transmission is calculated. Secondly, the received signal power of ZF-BF is represented as a function of the elements of the upper triangular matrix from QR decomposition of the channel matrix. Thirdly, we approximate the received signal power of ZF-BF with the SUS as the maximum of scaled chisquare random variables where the scaling factor is approximated as a function of both OLT and the number of users in the system. Putting all the above derivations and order statistics together, the approximated ergodic sum rate of ZF-BF with the SUS is shown in a closed form. The simulation results verify that the approximation tightly matches with the sample average for any OLT and even for a small number of users.

• Journal of computational fluids engineering
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• v.19 no.1
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• pp.47-56
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• 2014

Since a typical plate heat exchanger is made up of a huge number of unitary cells, it may be impossible to predict the aero-thermal performance of the full scale heat exchanger through three-dimensional numerical simulation due to the enormous amount of computing resources and time required. In the present study, a simple flow-network model using the friction factor correlation and a thermal-network model based on the effectiveness-number of transfer units (${\varepsilon}$-NTU) method has been developed. The complicated flow pattern inside the cross-corrugated heat exchanger has been modeled into flow and thermal networks. Using this model, the heat transfer between neighboring streams can be considered, and the pressure drop and the heat transfer rate of full-scale heat exchanger matrix are calculated. In the calculation, the aero-thermal performance of each unitary cell of the heat exchanger matrix was evaluated using correlations of the Fanning friction factor f and the Nusselt number Nu, which were calculated by unitary-cell CFD model.

• Korean Journal of Ichthyology
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• v.31 no.1
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• pp.16-22
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• 2019

Investigations on the study of the distribution aspects and extinction threat evaluation of the Korean endemic species, Iksookimia pacifica were done from 2017 to 2018 in Korea. During the study period, the samples of I. pacifica were collected in 17 streams, 46 sites (from Baebongcheon Stream of Goseong-gun to Gunsuncheon Stream of Gangneung-si) among the noted 33 streams and 104 sampling sites investigated. The population size of I. pacifica was relatively large in streams such as Bukcheon, Baebongcheon, Hwasangcheon, Cheonjincheon, Ohhocheon Stream etc., but the population size was small in streams such as Sacheoncheon, Namcheon, Gangneung Namdaecheon Stream etc. The main habitat of I. pacifica was the downstream pool of clean water with slow velocity and sand bottoms, and their sensibility was estimated to be due to river work and water pollution. Comparing the previous records of the appearance of I. pacifica, they were first seen in Sampocheon Stream, but they did not appear in Jusucheon, Jeoncheon, Samcheok Osipcheon Stream. Given this evidence as noted for the 19.5% reduction in occupancy within 3 generations, in small appearance range ($1,343km^2$) and small occupancy area ($184km^2$), the number of locations were many (18) and the population was relatively large within the range of habitat. Therefore, I. pacifica is now considered a Near Threatened (NT) based on the IUCN Red List categories and criteria.

• Korean Journal of Environment and Ecology
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• v.31 no.1
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• pp.72-80
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• 2017

Fish fauna and community structures in freshwater were analyzed in the streams (12 stations) of the Bogil Island from May to September 2015. Total numbers of the sampled species and genus (9 families) were 21 and 17, respectively. Gobiidae was the most dominant taxa, which accounted for 47.6% (10 species) of the total species, and the relative abundance, based on the number of individuals, was 60.4% (1,157 individuals). Subdominant families were three taxa of Cyprinidae (3 species; 500 ind.), Mugilidae (2 species; 168 ind.) and Mugilidae (2 species; 128 ind.). The dominant species, based on the relative abundance, was Rhynchocypris oxycephalus (20.7%) and the subdominant species were Gymnogobius urotaenia (19.5%), Leucopsarion petersii (17.2%) and Chelon haematocheilus (8.5%). These species were composed of upstream-resident fish as well as migratory fishes, so the streams of the Bogil Island had unique characteristics in the fish compositions. Based on all the species sampled, 9 species (42.9%) were primary freshwater fishes, 11 species (52.4%) were peripheral fishes and 1 species (4.8%) was amphidromous fish. Korean endemic species and exotic species were not found in the streams of Bogil Island. According to the analysis of fish community structure, species richness index and species diversity index were highest (1.831, 1.957) in the Site 8 and lowest in the Site 4. In the meantime, the dominance index was highestin the Site 4 (1.00) and lowest in theSite 8 (0.17).

• Journal of KIISE:Databases
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• v.37 no.1
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• pp.1-11
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• 2010

Recently, there has been a growing interest in the processing of continuous queries over multiple data streams. When the arrival rates of tuples exceed the memory capacity of the system, a load shedding technique is used to avoid the system becoming overloaded by dropping some subset of input tuples. In this paper, we propose an effective load shedding algorithm for multi-way windowed joins over multiple data streams. Most previous load shedding algorithms estimate the productivity of each tuple, i.e., the number of join output tuples produced by the tuple, based on its "join attribute value" and drop tuples with the lowest productivity. However, the productivity of a tuple cannot be accurately estimated from its join attribute value when the join attribute values are unique and do not repeat, or the distribution of the join attribute values changes over time. For these cases, we estimate the productivity of a tuple based on its "arrival order" on data streams, rather than its join attribute value. The proposed method can effectively estimate the productivity of a tuple even when the productivity of a tuple cannot be accurately estimated from its join attribute value. Through extensive experiments and analysis, we show that our proposed method outperforms the previous methods in terms of effectiveness and efficiency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.2
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• pp.269-286
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• 2011

In this paper, we study a problem that is concerning how to construct a delay-constrained multicast tree on a wireless mesh network (WMN) such that the number of serviced clients is maximized. In order to support high-quality and concurrent interference-free transmission streams, multiple radios are implemented in each mesh node in the WMNs. Instead of only orthogonal channels used for the multicast in the previous works, both orthogonal and partially overlapping channels are considered in this study. As a result, the number of links successfully allocated channels can be expected to be much larger than that of the approaches in which only orthogonal channels are considered. The number of serviced subscribers is then increased dramatically. Hence, the goal of this study is to find interference-free and delay-constrained multicast trees that can lead to the maximal number of serviced subscribers. This problem is referred as the MRDCM problem. Two heuristics, load-based greedy algorithm and load-based MCM algorithm, are developed for constructing multicast trees. Furthermore, two load-based channel assignment procedures are provided to allocate interference-free channels to the multicast trees. A set of experiments is designed to do performance, delay and efficiency comparisons for the multicast trees generated by all the approximation algorithms proposed in this study.

• Korean Journal of Environmental Biology
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• v.19 no.4
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• pp.282-291
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• 2001

The distribution and standing crop of phytoplankton were investigated seasonally at 6 stations in the nearby streams of Suwon sewage disposal plant. It turned out to be total of 176 taxa, and classified as 4 phylums, 4 classes, 11 orders, 6 suborders, 22 families, 54 genera, 155 species, 20 varieties and 1 form by Engler's classification system. Among 176 taxa, 22 including Microcystis Aphanizomenon flos-aquae were identified as indicators of water pollution. Standing crops of all stations investigated appeared to be relatively high as in other streams through the center of the city, such as Kyoungan-chon of Youngin-si and Gulpo-chon of Buchon-si. In station 1,2,4 and 6, the highest number of standing crop were shown in summer, while in station 3 and 5, it was high in winter. Based on the present study upon the distribution and standing crop of phytoplankton, it is regarded as the state of the eutrophication in the nearby streams of Suwon sewage disposal plant.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2859-2872
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• 2019

Interference alignment (IA) has been a powerful approach to achieve the maximum degree of freedom (DoF) for K users multiple-input-multiple-output (MIMO) interference channels. However, due to the feasibility constraint, aligning all the interference signals at each receiver is impractical for large K without symbol extension. In this paper, we propose two best-effort interference alignment (BEIA) schemes that the network selects the maximum number of interfering transmitters to align their signals given the feasibility conditions when each transmitter-receiver pair has a constant number of data streams. Besides, in case of not all interfering signals aligned at each receiver, an upper bound of the average throughput is derived. Simulation results show that the proposed schemes have superiority over the traditional methods, such as time division multiple access (TDMA) and cluster IA(CIA), in low and moderate signal-to-noise ratio (SNR) region in terms of average user throughput. In addition, the proposed max-min relative interference distance alignment scheme outperforms the proposed scheme of equal interfering transmitters number alignment in terms of both average user throughput and minimum user throughput.