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        검색결과 817

        181.
        2015.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Using black hole masses which span 105-1010M⊙, the distribution of galaxies in the (host spheroid stellar mass)-(black hole mass) diagram is shown to be strongly bent. While the core-Sersic galaxies follow a near-linear relation, having a mean Mbh=Msph mass ratio of ~0.5%, the Sersic galaxies follow a near-quadratic relation. This is not due to offset pseudobulges, but is instead an expected result arising from the long-known bend in the Msph-σ relation and a log-linear Mbh-σ relation.
        4,000원
        182.
        2015.09 KCI 등재 구독 인증기관·개인회원 무료
        This work considers the elliptic restricted three-body problem under effects of radiation of the bigger primary, and an oblate spheroid for the smaller primary to mimic an exoplanetary system with a gas giant planet. Under the in uences of both effects we look for the existence of the triangular equilibrium points and the in uences of the radiation and oblateness on the locations and motion of the points. We set the system in a normalized rotating coordinate system and derive equations of motion for the third infinitesimal object. Our study shows that the effects modify the equilateral/isosceles triangle shape with respect to the primaries. The triangular points also have non-planar motion with period depending on the value of the planet oblateness.
        183.
        2015.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Most of the stars in the Galaxy are in binary systems. Binaries should be possible as the hosting stars of planets. Searching for planetary companions to binaries, especially evolved close binary stars, can provide insight into the formation and the ultimate fate of circumbinary planets and shed light on the late evolution of binary stars. In order to do this, we have chosen some post common envelope binaries including sdB-type eclipsing binaries and detached WD+dM eclipsing binaries as our targets and monitored them for several years. In this paper, we will present some of our new observations and results for three targets, NSVS 07826147, NSVS14256825 and RR Cae.
        3,000원
        184.
        2015.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We investigated the period variation for 79 eclipsing binary systems using 20 years (1990-2009) of EROS, Macho, and OGLE survey observations. We discovered 9 apsidal motions, 8 mass transfers, 5 period increasing and decreasing systems, 12 light-travel-time effects, 5 eccentric systems and 40 other systems showing no period variations. We select 3 representative eclipsing binary systems; EROS 1052 for apsidal motion, EROS 1056 for mass transfer, and EROS 1037 for the light-travel-time effect. We determine the period variation rate (dP/dt), orbital parameters of the 3rd body (e3, ω3, f(m3), P3, T3), apsidal motion parameters (dω/dt, U, Ps, Pa, e) and apsidal motion period by analyzing the light curves and O-C diagrams.
        3,000원
        185.
        2015.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Due to the lack of an accretion disk in a polar (magnetic cataclysmic variable, MCV), the material transferred from the secondary is directly accreted onto the white dwarf, forming an accretion stream and a hot spot on the white-dwarf component. During the eclipses, different light components can be isolated. Therefore, the monitoring of eclipsing polars could provide valuable information on several modern astrophysical problems, e.g., CVs as planetary hosting stars, mass transfer and mass accretion in CVs, and the magnetic activity of the most rapidly rotating cool dwarfs. In the past five years, we have monitored about 10 eclipsing polars (e.g., DP Leo and HU Aqr) using several 2-m class telescopes and about 100 eclipse profiles were obtained. In this paper, we will introduce the progress of our research group at YNOs. The first direct evidence of variable mass transfer in a CV is obtained and we show that it is the dark-spot activity that causes the mass transfer in CVs. Magnetic activity cycles of the cool secondary were detected and we show that the variable mass transfer is not caused by magnetic activity cycles. These results will shed light on the structure and evolution of close binary stars (e.g., CVs and Algols).
        3,000원
        186.
        2015.06 구독 인증기관·개인회원 무료
        Peer pressure and popularity have always been important issues for teenagers, potentially impacting on teenagers’ attitudes towards luxury, social consumption motivation and their self-concept clarity (how clearly teens view themselves). We empirically investigate these relationships using data from a sample of Brazilian teens and find that self-concept clarity has a significant effect on peer pressure, popularity and social consumption motivation, which itself directly impacts attitudes towards luxury items. The total sample consisted of 558 teenagers between the ages of 12 and 19 (grades 7 through 12). Hypotheses were tested using structural equation modeling.
        187.
        2015.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The major limiting factor of the reproductive performance on many farms is the failure to detect estrus in a timely and accurate manner. The estrus detection for Hanwoo cows (Bos taurus coreanea) is generally performed by the visual observation which is estimated at about 40% detection rate only. This recurring problem among farmers has motivated the development of various estrus detection aids. The mounting event duration threshold, standing heat event frequency threshold, estrus detection algorithm and so on, are necessarily needed in order to detect the estrus of Hanwoo cows accurately when using some automatic devices. However, they are not yet investigated for Hanwoo cows. Therefore, the objective of this study was to establish a mounting event duration threshold and standing heat event frequency threshold more specifically for Hanwoo breed by discriminating the duration of standing heat mounting from shorter duration spurious mountings which routinely occur in cattle herds. One hundred and fifty Hanwoo cows with an age between 2 to 5 years were used in this study. Cows that were expected to come into estrus within 3days were randomly assigned to each compartment for the estrus group (EG). The heated cows were video recorded for about 24 hours until after post estrus. The results showed that Hanwoo cows can be considered on estrus when it stand immobile during mounted by any other cow in more than or equal to 3.15s and 3.22s in chest-tail head mount (CTM) and head-above back mount (HBM) and that occurs consecutively at least three times within 876.4s interval. The algorithm was also developed using the thresholds of the mount duration, mount interval and consecutive occurrence number.
        4,000원
        188.
        2015.06 구독 인증기관 무료, 개인회원 유료
        In the tanker industry, there are a lot of uncertain conditions that tanker companies have to deal with.For example, the global financial crisis and economic recession, the increase of bunker fuel prices and global climate change. Such conditions have forced tanker companies to change tankers speed from full speed to slow speed, extra slow speed and super slow speed. Due to such conditions, the objective of this paper is to present a methodology for determining vessel speeds of tankers that minimize the cost of the vessels under such conditions. The four levels of vessel speed in the tanker industry will be investigated and will incorporate a number of uncertain conditions. This will be done by developing a scientific model using a rule-based Bayesian reasoning method. The proposed model has produced 96 rules that can be used as guidance in the decision making process. Such results help tanker companies to determine the appropriate vessel speed to be used in a dynamic operational environmental.
        4,600원
        190.
        2015.04 구독 인증기관·개인회원 무료
        The genus Sphathius is belong to the subfamily Doryctinae in the family Braconidae and are described with >300 species in the world (Shenefelt and Marsh, 1976). This genus is distinguished from other winged Doryctinae by 1) forewings with three submarginal cells; 2) first subdiscal cell of forewing closed; and 3) first metasomal segment petiolate, widening apically, lacking basal wing-like projections, and inserted on propodeum near coxal bases (Marsh, 1997). For the purpose of finding the biological agent for Asian longhorned beetle (ALB; Anoplophora glabripennis (Motschulsky)) and Citrus longhorned beetle (CLB; A. chinensis (Förster)), we had installed the ALB- and CLB-infested sentinel logs to attract parasitoids at experimental field of the Korea National Arboretum during summer season in 2014. Several L1 and L2 CLB larvae were found attacked by braconid larvae that were reared to adult stage. Their larvae are identified to Spathius gwangneungensis sp. nov. belong to the Spathius exarator species group. This new species has special characteristics as following; Body reddish brown or dark reddish brown, body length 2.5~3.7mm and forewing length 2.2~3.0mm in female and body length 2.1~2.6mm and forewing length 1.5~2.0mm in male, hind femur distinctly transversely aciculate dorsally, forewing more or less infuscate with a longitudinal hyaline band medially, vein m-cu of hind wing interstitial, second tergite entirely sculptured without striation, and third to fifth tergites basally sculptured. Ovipositor sheath 0.6 times as long as metasoma.
        194.
        2014.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The objective of this study was to know the in vitro effects of supplemental anthelmintic plant extracts on the inhibition of protozoa for reducing methane production in the rumen. A fistulated Holstein cow was used as a donor of rumen fluid. The plant extracts (Lonicera japonica, Zanthoxylum piperitum, Pyrethrum, Torreya nucifera, Ruta graveolens) known to have anthelmintic effect were added to the in vitro fermentation bottles containing the rumen fluid and medium. The rumen protozoal population was depressed by the addition of Pyrethrum, Torreya nucifera and Ruta graveolens. The methane production was also significantly (p<0.05)reduced by addition of Pyrethrum (2.20 ml/g DM), Torreya nucifera (2.36 ml/g DM) and Ruta graveolens (2.20 ml/g DM). The microbial growth in the treatments of Ruta graveolens or anthoxylum piperitum was the greatest after 12 h and 24 h incubations, respectively. The results of this study indicated that anthelmintic plant extracts appeared to reduce methane production by inhibition of ruminal protozoa related with the methanogens living endosymbiotic in protozoal cells.
        4,000원
        196.
        2013.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Previously, we demonstrated the presence of a second copy of LPS myristoyl transferase in enterohemorrhagic Escherichia coli O157:H7, an important zoonotic diarrheagenic food-borne pathogen; the pO157-encoded ecf (an eae-conserved fragment) and the chromosomally-encoded lpxM (also referred to as msbM) genes. Although both genes share the same function as an LPS myristoyl transferase, the pO157-encoded ecf is thermoregulated via an intrinsically curved DNA while the chromosomal lpxM is regulated by the PhoP/Q two component regulatory system. However, it is unclear why E. coli O157: H7 carries two copies of LPS myristoyl transferase that are differentially regulated. In this study, a whole genome-scale transcriptome specific to E. coli O157:H7 was carried out for identification of the genes differentially expressed in the amyristoylated E. coli O157:H7. The results identified a total of 110 EHEC genes that were up- or down-regulated in the amyristoylated E. coli O157:H7 strain, including genes associated with virulence (26.36%), metabolism (20.91%), transport (10.91%), signal transduction (4.55%), genetic information processing (3.64%), stress response (2.73%), regulatory function (2.73%), motility/adherence (3.64%), cell envelope (2.73%), cell division (1.82%) and ORFs of unknown function (17.27%). Of particular interest, the expression of LEE pathogenicity island genes was significantly influenced by LPS structural defects.
        4,000원
        199.
        2013.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        An experiment was conducted to study effects of abomasal infusions of casein, glucose or starch on milk production and blood metabolites in dairy cows. Four lactating cows (559±41.9kg) fitted with 100 mm ruminal cannulas were used in a 4 × 4 Latin square experiment. The cows were given access ad libitum to grass silage and received 6.2 kg dry matter (DM) of a mixture of rapeseed meal (5.3kg/d DM) and barley grain (0.9kg/d DM) as a basal diet (CON), the basal diet plus intra-abomasal infusions of 270 g sodium caseinate (CAS), 300 g of glucose (GLU) or 243 g of starch (STA) starting at 09:00 h each day. Abomasal infusion of different nutrients did not affect (p>0.05) grass silage intake and rumen fermentation parameters (rumen pH, ammonia N and volatile fatty acids). As unexpected, milk yield and composition data did not differ between CON and the treated groups (p>0.05). Most of plasma amino acids were not significantly (p>0.05) affected by the abomasal infusions of CAS, GLU or STA except for histidine, tryptophan and glycine. Although histidine, known as the first limiting amino acid in dairy cows fed grass silage based diets, was significantly (p=0.003) increased by CAS, we failed to result in a clear increase in milk yield and protein yield. This discrepancy between plasma AA profiles and milk production could be presumably explained by relatively high concentration of total amino acids in the present study (2,039μmol/l).
        4,000원
        200.
        2013.04 구독 인증기관·개인회원 무료
        As nematologists we should ask ourselves how has nematode management changed or improved over the past 50 years. During this period we have lost over 12 key chemicals used as nematicides, some of which were highly efficacious. And in the meanwhile practically none have been added to our chemical control guides. This is problematic as we move into the future. For example, high value vegetable crops were highly dependent on methyl bromide for the past 40+ years. This product, whether used singly or in formulations mixed with chloropicrin, was highly efficacious against weeds, soilborne fungal diseases, and plant-parasitic nematodes. Now that the product is in very short supply, expensive, and allocated on the basis of critical use exemptions vegetable growers must begin to turn to other tactics. In 1994 scientist set a goal of developing a highly efficacious, reliable, and cost effective alternatives to methyl bromide but little success has been attained. The task was made difficult because of the lack of highly efficacious products, environmental constrains, worker protection issues, and newly imposed regulations that impact the use of soil fumigants. As a consequence we are moving toward a period when growers will be forced to choose less efficacious chemical products, if such products receive Federal registration, or choose other nematode management tactics. There has been only limited success with development of crop plants with resistance to plant-parasitic nematodes. Although promising, biological control has not yet made an impact on nematode management. Crop rotation, which has been listed as a control tactic for many years, remains one of the better choices for growers. Other tactics, e.g., solarization, organic amendments, and fallowing-flooding, etc have limited use. The pros and cons of each of these possible plant- parasitic nematode management tactics will be discussed.