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Before/After Precoding Massive MIMO Systems for Cloud Radio Access Networks
Park, Sangkyu,Chae, Chan-Byoung,Bahk, Saewoong The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.4
In this paper, we investigate two types of in-phase and quadrature-phase (IQ) data transfer methods for cloud multiple-input multiple-output (MIMO) network operation. They are termed "after-precoding" and "before-precoding". We formulate a cloud massive MIMO operation problem that aims at selecting the best IQ data transfer method and transmission strategy (beamforming technique, the number of concurrently receiving users, the number of used antennas for transmission) to maximize the ergodic sum-rate under a limited capacity of the digital unit-radio unit link. Based on our proposed solution, the optimal numbers of users and antennas are simultaneously chosen. Numerical results confirm that the sum-rate gain is greater when adaptive "after/before-precoding" method is available than when only conventional "after-precoding" IQ-data transfer is available.
Park, Sangkyu,Cho, Kang-Hyun The Korean Society for Integrative Biology 2003 Korean journal of biological sciences Vol.7 No.4
To quantify nutrient loading from emergent macrophytes through leaching in the littoral zones of Paldang Reservoir, we conducted incubation experiments using leaf litter of the emergent macrophyte, Zizaniz latifolia. To separate the leaching process from microbial decay, we used $HgCl_2$ to suppress microbial activity during the experiment. We measured electric conductivity, absorbance at 280nm, total nitrogen and dissolved inorganic nitrogen, total phosphorus and soluble reactive phosphorus, Na, K, Mg and Ca amounts in leaf litter and in water. In addition, we examined the effects of water temperature and ion concentrations of ambient water on the leaching process. A total of 6% of the initial ash-free dry mass of leaf litter was lost due to leaching during incubation (four days). Electric conductivity and A280 continued to increase and saturate during the incubation. To compare reaching rates of different nutrients, we fitted leaching dynamics with a hyperbolic saturation function [Y=AㆍX/(B+X)]. From these fittings, we found that ratios of leaching amounts to nutrient concentration in the litter were in the order of K > Na > Mg > P > Ca > N. Leaching from leaf litter of Z. latifolia was dependent on water temperature while it was not related with ion concentrations in the ambient water. Our results suggest that the leaching process of nutrients, especially phosphorus, from aquatic macrophytes provides considerable contribution to the eutrophication of the Paldang Reservoir ecosystem.
Plant Metabolomics for Plant Chemical Responses to Belowground Community Change by Climate Change
Park, Sangkyu,Seo, Young-Su,Hegeman, Adrian D. 한국식물학회 2014 Journal of Plant Biology Vol.57 No.3
General circulation models on global climate change predict increase in surface air temperature and changes in precipitation. Increases in air temperature (thus soil temperature) and altered precipitation are known to affect the species composition and function of soil microbial communities. Plant roots interact with diverse soil organisms such as bacteria, protozoa, fungi, nematodes, annelids and insects. Soil organisms show diverse interactions with plants (eg. competition, mutualism and parasitism) that may alter plant metabolism. Besides plant roots, various soil microbes such as bacteria and fungi can produce volatile organic compounds (VOCs), which can serve as infochemicals among soil organisms and plant roots. While the effects of climate change are likely to alter both soil communities and plant metabolism, it is equally probable that these changes will have cascading consequnces for grazers and subsequent food web components aboveground. Advances in plant metabolomics have made it possibile to track changes in plant metabolomes as they respond to biotic and abiotic environmental changes. Recent developments in analytical instrumentation and bioinformatics software have established metabolomics as an important research tool for studying ecological interactions between plants and other organisms. In this review, we will first summarize recent progress in plant metabolomics methodology and subsequently review recent studies of interactions between plants and soil organisms in relation to climate change issues.
New Recorded Species in Three Genera of the Sordariomycetes in Korea
( Sangkyu Park ),( Leonid Ten ),( Seung-yeol Lee ),( Chang-gi Back ),( Jae-jin Lee ),( Hyang Burm Lee ),( Hee-young Jung ) 한국균학회 2017 Mycobiology Vol.45 No.2
In an ongoing survey of Korean indigenous fungi, three fungal strains belonging to the Sordariomycetes were isolated from soil samples. These strains were designated KNU16-001, KNU16-002, and KNU16-009, and identified as Ambrosiella grosmanniae, Acremonium sclerotigenum, and Trichocladium asperum, respectively, based on morphological characterization and phylogenetic analysis using internal transcribed spacer region sequences of ribosomal DNA. This is the first report of these species in Korea.
Sporothrix stylites : A New Record from Field Soil in Korea
( Sangkyu Park ),( Seung-yeol Lee ),( Chang-gi Back ),( In-kyu Kang ),( Leonid Ten ),( Hyang Burm Lee ),( Hee-young Jung ) 한국균학회 2017 韓國菌學會誌 Vol.45 No.3
The fungal strain, designated KNU16-008, was isolated from field soil in Chungcheongnam-do, Korea. The isolated fungi was characterized by morphological and phylogenetic analyses. Isolated fungus showed typical morphological characteristics of the genus Sporothrix. Based on its phylogenic analysis using internal transcribed spacer (ITS) of rDNA and β-tubulin gene sequences, the strain KNU16-008 was identified as Sporothrix stylites. This species has not been previously reported in Korea.
First Report of Botryosphaeria parva Causing Stem Blight on Rubus crataegifolius in Korea
Park, Sangkyu,Kim, Seung-Han,Back, Chang-Gi,Lee, Seung-Yeol,Kang, In-Kyu,Jung, Hee-Young The Korean Society of Plant Pathology 2016 식물병연구 Vol.22 No.2
In 2015, stem blight of Rubus crataegifolius was observed in Pohang, Korea. The symptoms began as dark red spots in the stem, which led to stem blight, then leaf blight, and eventually resulted in death. A fungal isolate was obtained from a symptomatic stem and incubated on a potato dextrose agar plate. The isolated fungus produced white, cloudy mycelia turned black in 3 days. Based on the morphological characteristics, the causal fungus was assumed to be Botryosphaeria sp. A pathogenicity test was conducted according to Koch's postulates. To identify the causal agent, the combined sequence of the internal transcribed spacer, ${\beta}$-tubulin, and translation elongation factor $1{\alpha}$ genes were used for phylogenetic analysis. Approximately 1,200 bp of the combined sequence clearly suggested that the isolated pathogen was Botryosphaeria parva. This is the first report on stem blight in R. crataegifolius caused by B. parva in Korea.