• Journal of The Korean Astronomical Society
• /
• v.48 no.3
• /
• pp.191-194
• /
• 2015

Massive gravity provides a natural solution for the dark energy problem of cosmology and is also a candidate for resolving the dark matter problem. I demonstrate that, assuming reasonable scaling relations, massive gravity can provide for Milgrom’s law of gravity (or “modified Newtonian dynamics”) which is known to remove the need for particle dark matter from galactic dynamics. Milgrom’s law comes with a characteristic acceleration, Milgrom’s constant, which is observationally constrained to a₀ ≈ 1.1 × 10⁻¹⁰ ms⁻² . In the derivation presented here, this constant arises naturally from the cosmologically required mass of gravitons like , with Λ, H₀, and Ω_Λ being the cosmological constant, the Hubble constant, and the third cosmological parameter, respectively. My derivation suggests that massive gravity could be the mechanism behind both, dark matter and dark energy.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.2
• /
• pp.42.1-42.1
• /
• 2014

Neutrino science has received a boost of attention quite recently in cosmology, since the outstanding discovery in particle physics over the last decade that neutrinos are massive: pinpointing the neutrino masses is one of the greatest challenges in science today, at the cross-road between particle-physics, astrophysics, and cosmology. Cosmology offers a unique 'laboratory' with the best sensitivity to the neutrino mass, as primordial massive neutrinos comprise a small portion of the dark matter and are known to significantly alter structure formation. I will first introduce a new suite of state-of-the-art hydrodynamical simulations with cold dark matter, baryons and massive neutrinos, specifically targeted for modeling the low-density regions of the intergalactic medium as probed by the Lyman-Alpha forest at high-redshift. I will then present and discuss how these simulations are used to constrain the parameters of the LCDM cosmological model in presence of massive neutrinos, in combination with BOSS data and other cosmological probes, leading to the strongest bound to date on the total neutrino mass.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.458-461
• /
• 2006

Early age cracking of concrete is a widespread and complicated problem, and diverse applications in practical engineering have focused on this issue. Since massive concrete base slab composes the infrastructure of other concrete structures such as pier, concrete dam, and high rise buildings, early age cracking of that is considered as a crucial problem. In this study, finite element analysis (FEA) implemented with the age-dependent microplane model was performed. For a massive concrete base slab, cracking initiation and propagation, and deformation variation were investigated with concrete age. In massive concrete slab, autogenous shrinkage increases the risk of early age cracking and it reduces reinforcement effect on control of early age cracking. Gradual crack occurrence is experienced from exterior surface towards interior of the slab in case of combined hydration heat and autogenous shrinkage. FEA implemented with enhanced microplane model successfully simulates the typical cracking patterns due to edge restraint in concrete base slab.

• Journal of information and communication convergence engineering
• /
• v.16 no.1
• /
• pp.17-22
• /
• 2018

In massive multiple-input multiple-output (MIMO) systems, linear channel estimation algorithms are widely applied owing to their simple structures. However, they may cause pilot contamination, which affects the subsequent data detection performance. Therefore, herein, for an uplink multicell massive multiuser MIMO system, we consider using an alternating projection (AP) for channel estimation to eliminate the effect of pilot contamination and improve the performance of data detection in terms of the bit error rates as well. Even though the AP is nonlinear, it iteratively searches the best solution in only one dimension, and the computational complexity is thus modest. We have analyzed the mean square error with respect to the signal-to-interference ratios for both the cooperative and non-cooperative multicell scenarios. From the simulation results, we observed that the channel estimation results via the AP benefit the following signal detection more than that via the least squares for both the cooperative and non-cooperative multicell scenarios.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.1
• /
• pp.41.2-41.2
• /
• 2012

It has been suggested that merging plays an important role in the formation and the evolution of early-type galaxies (ETGs). Optical-NIR color gradients of ETGs in high density environments are found to be less steep than those of ETGs in low density environments, hinting frequent merger activities in ETGs in high density environments. In order to examine if the flat color gradients are the result of dry mergers, we studied the relations between merging features, luminosities, environments and color gradients of 196 low redshift ETGs selected from Sloan Digital Sky Survey (SDSS) Stripe82. Near Infrared (NIR) images are taken from UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Color (r-K) gradients of ETGs with tidal features are a little flatter than relaxed ETGs, but not significant. We found that massive (> 10^11.3 solar masses) ETGs have -40% less scattered color gradients than less massive ETGs. The less scattered color gradients of massive ETGs could be evidence of dry merger processes in the evolution of massive ETGs. We found no relation between color gradients of ETGs and their environments.

• Clinics in Shoulder and Elbow
• /
• v.17 no.1
• /
• pp.44-47
• /
• 2014

Typically, massive rotator cuff tears have stiff and retracted tendon with poor muscle quality, in such cases orthopaedic surgeons are confronted with big challenging to restore the cuff to its native footprint. Furthermore, even with some restoration of the footprint, it is related with a high re-tear rate due to less tension free repair and less tendon coverage. In this tough circumstance, the partial repair has yielded satisfactory outcomes at relatively short follow-up by re-creating the transverse force couple of the rotator cuff. Through this partial repair, the massive rotator cuff tear can be converted to the "functional rotator cuff tear" and provide improvement in pain and functional outcomes in patient's shoulder.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1992.04a
• /
• pp.143-147
• /
• 1992

Description of the behavior of the R.C structural members fixed on massive concrete is not normally generalization of recognized configuration for regular R.C. design guidanes. This can be due to the complexity of evaluation of internal resistancy and deflection changes of the members subjected to the various external forces. On the base of axially loaded member fixed on footing, however, the estimation of deflection changes due to flexural force shear force and rotational force is to be carried out in ways of specifying the bond characteristics of axial bars embedded in massive concrete. This work is to quantify adhesion of steel-concrete, initial concrete cracking stress near bar rib, maximum bond stress and residual stress in concrete respectively. In addition to quantification of them for particulate behavior, the suggestions of multi-linear bond stress-slip diagram made in carrying out finite element analyses for adhesion failure, examining concrete cracking status and reviewing existing experimental data lead to alternatively constructed relationship between bond stress and slip for a axial bars embedded massive concrete.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.69.2-69.2
• /
• 2016

We study the environmental dependence of the mass-size relation for the most massive early type galaxies (M>$10^{10.7}M_{\odot}$) in the redshift range 0.10~0.15. The sizes of galaxies are measured by non-parametric method. We find that galaxies more massive than $10^{11.1}M_{\odot}$ show the environmental dependence in the mass-size relation. The galaxies with M>$10^{11.1}M_{\odot}$ located in the densest, cluster like environment have larger sizes and extended surface brightness profiles than their counterparts located in a low dense environment. We also find that the environmental dependence of the mass-size relation is more significant for the brightest cluster galaxies (BCGs) than non-BCGs. We use the semi analytic galaxy formation simulation based on the Millennium 1 Simulation for interpretation. Our result can be explained with a hierarchical growth of the most massive galaxies through dissipation-less merger in dense environment.

• Clinics in Shoulder and Elbow
• /
• v.22 no.1
• /
• pp.50-57
• /
• 2019

Rotator cuff tear is a common cause of shoulder pain and disability in adults. Due to the various nature of progression of rotator cuff tears and the complex biomechanics of the shoulder joint, repair and treatment of large-to-massive tears are challenging for many surgeons. Despite the recent popularity of reverse total shoulder arthroplasty as a treatment option for large-to-massive irreparable rotator cuff tears, biological and mechanical repair augmentation has also shown promise as a viable treatment option. The purpose of this study was to briefly summarize and review current studies on the assessment and arthroscopic treatment of large-to-massive rotator cuff tears, whether repairable or irreparable, to aid in developing a consensus on future treatment directions.

• Journal of Korean Neurosurgical Society
• /
• v.65 no.2
• /
• pp.325-330
• /
• 2022

Various grading systems and surgical techniques have been developed for the treatment of intraventricular hemorrhage (IVH); however, little attention has been paid to the fourth ventricle hematoma. Nonetheless, hemorrhagic dilation of the fourth ventricle may lead to catastrophic consequences for patients with massive IVH. We present two cases of massive IVH accompanied by massive fourth ventricle hematoma which was successfully removed with combination of suboccipital craniotomy for fourth ventricle hematoma and intraventricular fibrinolysis for supratentorial hematoma.