• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.4
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• pp.27-37
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• 2008

It is most serious problem which is various occurs from the agricultural concrete structure and off shore concrete structure the problem which it comes to think is deterioration of the concrete which is caused with the corrosion of the reinforcing steel which is caused by with permeation of the water and the sea water. Specially the off shore concrete structure has been deteriorated by the steel reinforcement corrosion. The latex modified concrete(LMC) was adds latex in the plain concrete as the latex has increase the durability of concrete. This study were accomplished to the estimate the diffusion coefficient of LMC, and the time dependent constants of diffusion. The average chloride diffusion coefficient was estimated. Also, the average chloride diffusion coefficient was compared with diffusion coefficient test results of 28 curing days. The test results indicated that the average chloride diffusion coefficient could closely estimate the test results of the diffusion coefficient test results of 28 curing days.

• Journal of Astronomy and Space Sciences
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• v.35 no.1
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• pp.19-30
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• 2018

The analysis of the high-resolution spectra of 31 Magellanic Clouds Cepheid variables enabled the identification of thorium lines. The abundances of thorium were found with spectrum synthesis method. The calculated thorium abundances exhibit correlations with the abundances of other chemical elements and atmospheric parameters of the program stars. These correlations are similar for both Clouds. The correlations of iron abundances of thorium, europium, neodymium, and yttrium relative to the pulsational periods are different in the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC), namely the correlations are negative for LMC and positive or close to zero for SMC. One of the possible explanations can be the higher activity of nucleosynthesis in SMC with respect to LMC in the recent several hundred million years.

• International Journal of Highway Engineering
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• v.3 no.4 s.10
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• pp.93-103
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• 2001

This study focused on the field applicability evaluation of SB latex-modified concrete (LMC) for concrete bridge deck overlay using mobile mixer. The main experimental factors were water-cement ratio(31, 33, 35 37%), latex contents(0, 5, 10, 15, 20%), and fine aggregate ratio(55, 56, 57, 58%) in order to evaluate the workability, mechanical properties, and durability property of LMC. The slump loss, air content, compressive and flexible strength tests were used to evaluate LMC workability and strength properties. Also, the rapid chloride permeability test was used to evaluate the relative permeability of LMC. As a results, the LMC with enough workability and good quality was produced when it was mixed in field using mobile mixer, satisfying the target compressive strength and flexural strength. The required water-cement ratio of LMC for same workability when mixing with mobile mixer was less than that when mixing in laboratory. Increasing the amount of latex produced concrete with increased flexural strength by mobile mixer. The required cement-water ratios for same initial $19{\pm}3cm$ slump were 37% and 33% at laboratory and mobile mixer, respectively. The mobile mixer was accurately calibrated satisfying the required specification.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.3
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• pp.199-204
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• 2014

We conducted a short-term incubation experiment in order to understand the effect of the salinity of reclaimed coastal soils on nitrogen mineralization of livestock manure compost (LMC). Two soils with the same soil texture but different EC levels were collected from the same field. These samples were treated with 0%, 1%, 2%, and 3% of LMC by weight basis and incubated at $25^{\circ}C$ to observe changes in inorganic N contents, pH, and dehydrogenase activity with respect to time. As a result, regardless of the soil EC level, as the LMC increased, the total content of the inorganic N ($NH_4{^+}+NO_3{^-}$) increased. Difference in the soil EC level did not affect N mineralization of LMC greatly. The soil EC had negligible effect on the dehydrgenase activity as with the case of inorganic nitrogen. The $NH_4{^+}$ contents remained very low throughout the experimental period starting from the first week of incubation. We believe this is due to the high pH level (pH 7.9 and pH 8.3) of the original soils leading to ammonia volatilization. On the other hand the $NO_3{^-}$ content maintained high level as the LMC treatment level increased and reached maximum at the third week. The pH of the soil during incubation period decreased as the $NO_3{^-}$ contents increased and increased slightly after three weeks. The rise of pH level is believed to be from the $NO_3{^-}$ absorption for immobilization by microbes. In conclusion, the high soil $EC_{1:5}$ level of $12dS\;m^{-1}$ conducted in this experiment did not affect the growth in terms of soil microbes involved in N mineralization of LMC.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.252-255
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• 2009

This paper proposes a new loss minimization controller (LMC) for induction motor drive. The proposed LMC presents a strategy to minimize the total power losses of induction motor (IM), which is based on simplified equivalent circuit and simplified model of IM. The proposed controller using the field oriented control (FOC) method is to determine an optimal rotor flux for obtaining the minimum total power losses and higher efficiency. Simulation and experimental results are given to validate the effectiveness of the proposed method.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.93-94
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• 1996

The Galaxy and the Large and Small Magellanic Clouds (LMC and SMC respectively) form a triple system of mutually interacting galaxies. We have carried out a set of N-body simulations on the gravitational interaction of the SMC with the Galaxy and the LMC in order to model prominent features such as the Magellanic Stream, the inter-Cloud Bridge, and the large depth of the SMC which are thought to be products of the tidal interactions among the members of this system.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.595-597
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• 2015

LMC X-4 is an eclipsing high-mass X-ray binary exhibiting a superorbital modulation with a period of ~ 30:5 days. We present a detailed study of the variations of the superorbital modulation period with a time baseline of ~ 18 years. The period determined in the light curve collected by the Monitor of All-sky X-ray Image (MAXI) significantly deviates from that observed by the All Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE). Using the data collected by RXTE/ASM, MAXI, and the Burst Alert Telescope (BAT) onboard Swift, we found a significant period derivative, $\dot{P}=(2.08{\pm}0.12){\times}10^{-5}$. Furthermore, the O{C residual shows complex short-term variations indicating that the superorbital modulation of LMC X-4 exhibits complicated unstable behaviors. In addition, we used archive data collected by the Proportional Counter Array (PCA) on RXTE to estimate the orbital and spin parameters. The detected pulse frequencies obtained in small time segments were fitted with a circular orbital Doppler shift model. In addition to orbital parameters and spin frequency for each observation, we found a spin frequency derivative of $\dot{v}=(6.482{\pm}0.011){\times}10^{-13}Hz{\cdot}s^{-1}$. More precise orbital and spin parameters will be evaluated by the pulse arrival time delay technique in the future.

• Journal of Industrial Technology
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• v.25 no.B
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• pp.73-80
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• 2005

Durability of concrete structures is seriously compromised by cracking at early-age concretes, particularly in high-strength or high-performance concrete structures. Since early-age cracking is influenced by various factors that affect the hydration process, early-age shrinkage and stress/strain development, the behavior at early-age is highly complex and no rational methodologies for its control have yet been established. Concrete structures often present volumetrical changes particularly due to thermal and moisture related shrinkages. Volumetric instability is detrimental to the performance and durability of concrete structures because structural elements are usually restrained. These restrained shrinkages develope tensile stresses which often results in cracking in combination with the low fracture resistance of concrete. Early-age defects in high-performance concrete due to thermal and autogenous deformation shorten the life cycle of concrete structures. Thus, it is necessary to examine the behavior of early-age concrete at the stages of design and construction. The purpose of this study was to propose a shrinkage models of VES-LMC (very-early strength latex-modified concrete) at early-age considering thermal deformation and autogenous shrinkage.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.30.1-30.1
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• 2016

We have estimated a metallicity map of the Large Magellanic Cloud (LMC) using the Magellanic Cloud Photometric Survey (MCPS) and Optical Gravitational Lensing Experiment (OGLE III) photometric data. This is a first of its kind, high-spatial resolution map of metallicity up to a radius of $4^{\circ}-5^{\circ}$, derived using large area photometric data and calibrated using spectroscopic data of Red Giant Branch (RGB) stars. The RGB is identified in the V, (V - I) colour- magnitude diagrams of small subregions of varying sizes in both data sets. The slope of the RGB is used as an indicator of the mean metallicity of a subregion, and it is calibrated to metallicity using spectroscopic data for field and cluster red giants in selected subregions. The mean metallicity of the LMC is found to be [Fe/H] = -0.37 dex (${\sigma}[Fe/H]=0.12$) from MCPS data, and [Fe/H] = -0.39 dex (${\sigma}[Fe/H]=0.10$) from OGLE III data. The bar is found to have an uniform and higher metallicity compared to the disk, and is indicative of an active bar in the past. Both the data sets suggest a shallow radial metallicity gradient up to a radius of 4 kpc ($-0.049{\pm}0.002$ dex kpc-1 to $-0.066{\pm}0.006$ dex kpc-1). This metallicity gradient of the LMC disk, though shallow, resembles the gradient seen in spiral galaxies, and similar to that found in our Galaxy.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.54.3-55
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• 2017

The nature and physical environments of SNRs are diverse, and for this reason, the understanding of the properties of nearby SNRs is useful in interpreting the emission from SNRs in remote galaxies where we cannot resolve them. In this regard, the LMC is a unique place to study SNRs due to its proximity, location, and composition compared with our galaxy. We carried out a multi-wavelength study of SNR N63A in the LMC, a young remnant of the SN explosion of one of the most massive (> 40 Msun) stars in a cluster. It is currently expanding within a large H II region formed by OB stars in the cluster and engulfing a molecular cloud (MC). As such, N63A is a prototypical SNR showing the impact of SN explosion on the cluster and its environment. Its morphology varies strongly across the wave bands, e.g. the size in X-ray is three times larger than in optical. However, the bright optical nebula would correspond to a MC swept up by the SNR, and consequently the interaction SNR-MC is limited to the central portion of the SNR. We aimed to study the overall structure of N63A, using near-IR imaging and spectroscopic observations to obtain the physical parameters of the atomic shocks, and also to understand how the SNR- MC interaction works and reveal the structure of the shocked cloud as well as the consequences of the impact of the SNR shock on the MC, comparing information obtained in different wavelengths.