• 천문학회보
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• 제44권2호
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• pp.53.2-53.2
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• 2019

The genus of the matter density eld, as traced by galaxies, contains information regarding the nature of dark energy and the fraction of dark matter in the Universe. In particular, this topological measure is a statistic that provides a clean measurement of the shape of the linear matter power spectrum. As the genus is a topological quantity, it is insensitive to galaxy bias and gravitational collapse. Furthermore, as it traces the linear matter power spectrum, it is a conserved quantity with redshift. Hence the genus amplitude is a standard population that can be used to test the distance-redshift relation. In this talk, I present measurements of the genus extracted from the SDSS DR7 LRGs in the local Universe, and also slices of the BOSS DR12 data at higher redshift. I show how these combined measurements can be used to place cosmological parameter constraints on m, wde.

• 농업과학연구
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• 제46권1호
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• pp.125-135
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• 2019

Late-maturing Dark Horse, and early-maturing High Speed oat varieties were seeded on March 3, 2016 and harvested on three periods: May 31, June 10, and June 20 coded as early, mid, and late-harvest, respectively. Dried and ground samples were subjected to chemical analysis to determine nutritional values such as crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), ether extract (EE), organic matter (OM), and total digestible nutrient (TDN). Effective degradability (ED) of nutrients and fermentation characteristics including volatile fatty acid (VFA) composition, pH, gas production, and ammonia-N concentration were evaluated through an in vitro digestion method. Varieties of oat hays showed significant difference in terms of nutritional value, ED, and fermentation characteristics. Dark Horse showed higher CP and OM, and lower EE contents than High Speed. Dark Horse also showed higher EDDM (dry matter), NDF, ADF, and OM than High Speed, and although High Speed showed higher pH and ammonia-N, it had lower gas and total VFA production than Dark Horse. However, in terms of harvest period, significant difference was only observed in Dark Horse where early-harvest increased the CP, and late-harvest increased the NDF and OM contents. In addition, early-harvest of Dark Horse increased the EDDM and EDNDF of the forage. Therefore, early-harvest of late-maturing Dark Horse would give better nutrient efficiency than High Speed. Allowing Dark Horse to advance in maturity would decrease its nutrient productivity and efficiency.

• 천문학회보
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• 제40권1호
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• pp.80.3-81
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• 2015

Globular clusters (GCs) are known to have a very small amount of or no dark matter (DM). Several studies propose that GCs may have formed in individual dark halos. Thus, some of the current GCs might have a non-negligible DM content. Using the Fokker-Planck (FP) calculations, we investigate the dynamical evolution of the Galactic GCs residing in mini DM halo. We trace the initial amount of DM of 47 Tuc, NGC 1851, and M15, which is a 'disk/bulge' cluster, an 'old halo' cluster, and a 'young halo' cluster, respectively. We find that the three GCs have initially insignificant amounts of DM, less than 20 percent of the initial stellar mass of the each cluster.

• 천문학회보
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• 제37권1호
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• pp.39.2-39.2
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• 2012

We present our study on a comparison of dark matter halo merger history from the runs using different numerical simulation codes. To analyze the uncertainty caused by the use of different N-body calculation methods, we compare the results from two cosmological hydrodynamic simulation codes GADGET-2 and RAMSES, which use a TreePM algorithm and the Adaptive Mesh Refinement(AMR) technique respectively. We perform cosmological dark matter-only simulations with the same parameter set and initial condition for both. The dark matter halo mass functions from two simulation runs correspond well with each other, except for lower mass haloes. The discrepancy on the low-mass haloes in turn causes a notable difference in halo merger rate, especially for the case of extremely minor merger. The result from GADGET-2 predicts that most haloes undergo more number of mergers with small haloes than that from RAMSES, independent of halo mass and environment. However, in the context of the study on galaxy evolution, such extreme minor mergers generally do not have strong effects on galaxy properties such as morphology or star formation history. Hence, we suggest that this uncertainty could be quantitatively negligible, and the results from two simulations are reliable even with only minor difference in merger history.

• 천문학회보
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• 제38권1호
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• pp.34.2-34.2
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• 2013

Spin distribution of dark matter halos in a cosmological N-body simulation is well fitted by a log-normal distribution, but the origin of the log-normal like shape is still unknown. To understand the evolution of spin and the origin of spin distribution, we have studied the change of the angular momentum of simulated halos through their merging histories. First, we traced merging histories of the dark matter halos and measured the probability distribution of the angular momentum changes from a series of simulations. We were able to fit the angular momentum changes with the Gaussian distribution in spaces of M, spin, ${\Delta}M$. Using the simulated merging trees and the distribution of angular momentum changes during the merging events, we can recover the spin distribution of halos over the various mass scales.

• 한국환경과학회지
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• 제6권3호
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• pp.285-291
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• 1997

In order to Investigate the adsorption characteristics of organochlorine pesticides chlorothaloul and dicofol with soul colors and re참tons far souls of an orange orchard, the souls were sampled at 3 re삼tons, respectively. among black volcanic, dark brown volcanic, and broom nonvolcanlc sorts. Every so6 has a higher clay proportion (49-75%) In sol tcuture and the organic carbon content and cation ekchange capacity with soil decreased in the following sequence: Black volcanic > Dark brown volcanic > Brown nonvolcanic sorts. Especially those In black volcauc trolls were much higher than others. The retention time, quantitative detection limit, and extractian , efficiencies of chlorothalonil and dicofol were 2.82min, 1.5ng/mL, 93.6% and 3.64min, 4.5ng/mL. 94 2%, repectlvely. The Freundlich constant, Kd, was higher in dicofol compared to chlorothalonil and In the black volcanic souls that have higher organic carbon content and cation Bkchange capacity. The Freundlich constant, 1 In, was In the range of 0.76-0.89 In the black volcanic sorts that have a higher organic matter(16.4-19.8%), whereas It was In the range of 1.02-1.13 In the brown nonvolcanic souls that have a lower organic matter(2.4-3.4%), and so It was considered that 1 In was dependent on the organic matter.

• 천문학회보
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• 제41권2호
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• pp.63.4-64
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• 2016

We aim to investigate inflow history of matters that fall into the satellite systems around a dwarf galaxy in Lambda-Cold Dark Matter model. Each satellite system has unique properties because all satellite systems have different mass inflow history by environments and/or the events such as cosmic reionization and merging with other halos. To trace mass inflow history of the satellite systems, we perform three different cosmological zoom simulations whose galaxy mass is ${\sim}10^{10}M_{sun}$. Each initial zoom simulation covers a cubic box of $1Mpc/h^3$ with 17 million particles. Particle mass for dark matter (DM) and gas components is $M_{DM}=4.1{\times}10^3M_{sun}$ and $M_{gas}=7.9{\times}10^2M_{sun}$, respectively. Thus, each satellite system is resolved with more than hundreds - thousands of particles. We analyze the influence of the gravitational interaction with host galaxy, baryonic matter inflow by various cooling mechanisms, and merging events with other halos on the mass inflow history of satellite systems.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 1999년도 임시총회 및 가을 학술발표회 초록집 The Korean Environmental Sciences Society
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• pp.221-223
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• 1999

The adsorption and leaching of organophosphorus pesticide, EPN are investigated in Namwon soil(black volcanic soil), Aewol soil(very dark brown volcanic soil) and Mureung soil(dark brown nonvolcanic soil) sampled in Cheju Island. The organic matter of Namwon soil, Aewol soil and Mureung soil is 19.8%, 6.2%, 2.4%, respectively. The cation exchange capacity of Namwon soil, Aewol soil and Mureung soil is 24.8 meq/100g, 13.0 meq/100g, 9.5 meq/100g, respectively. The Freundlich constant, K value, is 89.4, 26.9 and 9.25 for Namwon soil, Aewol soil and Mureung soil, respectively. The K value of Namwon soil with very high organic matter content and cation exchange capacity was the highest for Aewol soil and Mureung soil. The Freundlich constant, 1/n, show a high correlation with organic matter content, i.e., it is less than unity for organic matter rich soil of Namwon soil and greater than unity for organic matter poor soil of Mureung soil. The leaching of EPN is slower for Namwon soil with high K values, and faster for Mureung soil with low K values. The results of the study is demonstrated the potential of pollution for EPN have little leached into soil environment.

• 천문학회보
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• 제39권1호
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• pp.32.1-32.1
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• 2014

Astronomical observations strongly suggest that the expansion rate of our universe is currently under acceleration. The nature of the so-called dark energy causing the acceleration is unknown, and it is one of the fundamental mysteries in the present day theoretical cosmology. Here we briefly review the current state of cosmic dark energy research in both theoretical and observational sides. Constraints on dynamical dark energy models (e.g., w-fluid, quintessence, and modified gravity) with recent observational data from type Ia supernovae, cosmic microwave background radiation, and large-scale structures in the universe indicate a preferred direction toward the simplest ${\Lambda}$CDM world model. We also discuss some issues regarding the early dark energy model and the spherical collapse of matter in the presence of dark energy.

• 천문학회보
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• 제32권2호
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• pp.22-22
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• 2007