• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.217-226
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• 2005

This study made member specimen for taking specimen, core with the concrete mixing normal concrete, admixture and conducted the same air curing as field conditions. After performing destructive and nondestructive test by age, estimate expression was suggested by analyzing correlations between compressive strength, rebound number and ultrasonic pulse velocity and the results are as follows. As a result of comparing error rate of existing expressions and this estimation expression, error rate of this estimation is reduced compared to existing expressions and has higher reliability. When conventional concrete expression is applied to admixture concrete, error rate occurs and then this study suggests the estimation expressions depending on types of admixture concrete.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2246-2253
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• 2011

This paper presents the error correction method of magnetic position sensor using recursive least square method (RLSM) with forgetting factor. Magnetic position sensor is proposed for linear position detection of the linear motor which has tooth shape stator, consists of permanent magnet, iron core and linear hall sensor, and generates sine and cosine waveforms according to the movement of the mover of the linear motor. From the output of magnetic position sensor, the position of the linear motor can be detected using arc-tan function. But the variation of the air gap between magnetic position sensor and the stator and the error in manufacturing process can cause the variation in offset, phase and amplitude of the generated waveforms when the linear motor moves. These variations in sine and cosine waveforms are changed according to the current linear motor position, and it is very difficult to compensate the errors using constant value. In this paper, the generated sine and cosine waveforms from the magnetic position sensor are compensated on-line using the RLSM with forgetting factor. And the speed observer is introduced to reduce the effect of uncompensated harmonic component. The approaches are verified by some simulations and experiments.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.55-59
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• 1999

The Rapid Expansion of Supercritical fluid Solutions (RESS) process was applied to particles coating. Microcapsules prepared by spray drying were used as the core particles, and two kinds of paraffin were used as the coating materials. Supercritical $CO_{2}$ solutions of paraffin were expanded through the short nozzle into the bed that was fluidized by air. Extraction temperature and pressure were varied at $50~120^{\circ}C$, $150~200\;kg/\textrm{cm}^2$, respectively. The thickness of theoritical coating layer ws measured, and precipitate coating layer on surface was analyzed by using SEM, FT-IR. The release behaviors of $Mg^{2+}$ ions were inspected by atomic absorbance spectrophtometer.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.225-229
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• 2017

This paper describes the loss analysis based on load conditions of the air conditioning compressor motors using variable dc-link voltage. The losses of PMSM (Permanent Magnet Synchronous Motor) should be analyzed by the PWM (Pulse Width Modulation) output of inverter. The harmonic loss by the PWM cannot consider that using the current source analysis of the inverter. In addition, when the voltage of dc-link is variable with the condition of variable speed and load conditions in motor, the losses of motor are also changeable, however it is hard to analyze those losses by only electromagnetic finite element method (FEM). Therefore, this paper proposes the analysis method considering the carrier frequency of the inverter and the varying state of the dc-link voltage through the FEM-control coupled analysis. Using proposed analysis method, additional core loss and eddy current loss of permanent magnet caused by PWM could be analyzed. Finally, the validity of the proposed analysis method is verified through the comparison the result of coupled analysis with experiment.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.219-229
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• 2015

Objective : The purpose of this study was to analyze EMG according to surface type and elastic band usage during the pilates Superman movement. Method : The subjects were 10 female university students with a mean age of 27. The independent variables were surface type (yoga mat, air filled equipment, elastic mat) and elastic band usage. In order to measure muscle activity, the Noraxon(USA) was used. Eight muscles (upper trapezius, lower trapezius, thoracic spine, lumbar spine, gluteus maximus, gluteus medius, biceps femoris, semitendinosus) activation were analyzed. For the statistical analysis, MANOVA, independent t-test and Scheffe test for the post-hoc via SPSS 20.0 was used. Results : The left and right upper trapezius muscle activities were significantly reduced when using the elastic bands. In addition gluteus medius muscle activities significantly increased with the elastic band as well. Conclusion : According to the usage of the elastic band and the different types of surfaces, different muscle groups were recruited. Elastic bands were found to have more activation on the gluteus medius muscle meanwhile there was less activation on the upper trapezius during the pilates Superman movement.

• Journal of the Korean earth science society
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• v.39 no.1
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• pp.1-22
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• 2018

Eight different data sets are examined in order to gain insight into the surface heat flux traits of the East Asian marginal seas. In the case of solar radiation of the East Sea (Japan Sea), Coordinated Ocean-ice Reference Experiments ver. 2 (CORE2) and the Objectively Analyzed Air-Sea Fluxes (OAFlux) are similar to the observed data at meteorological stations. A combination is sought by averaging these as well as the Climate Forecast System Reanalysis (CFSR) and the National Centers for Environmental Prediction (NCEP)-1 data to acquire more accurate surface heat flux for the East Asian marginal seas. According to the Combination Data, the annual averages of net heat flux of the East Sea, Yellow Sea, and East China Sea are -61.84, -22.42, and $-97.54Wm^{-2}$, respectively. The Kuroshio area to the south of Japan and the southern East Sea were found to have the largest upward annual mean net heat flux during winter, at -460- -300 and at $-370--300Wm^{-2}$, respectively. The long-term fluctuation (1984-2004) of the net heat flux shows a trend of increasing transport of heat from the ocean into the atmosphere throughout the study area.

• Journal of Mechanical Science and Technology
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• v.14 no.8
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• pp.879-890
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• 2000

This study investigates the nonpremixed $H_2/CO$-air turbulent flames numerically. The turbulent combustion process is represented by a reaction progress variable model coupled with the presumed joint probability function. In the present study, the turbulent combustion model is applied to analyze the nonadiabatic flames by introducing additional variable in the transport equation of enthalpy and the radiative heat loss is calculated using a local, geometry independent model. Calculations are compared with experimental data in terms of temperature, and mass fraction of major species, radical, and NO. Numerical results indicate that the lower and higher fuel-jet velocity flames have the distinctly different flame structures and NO formation characteristics in the proximity of the outer core vortex zone. The present model correctly predicts the essential features of flame structure and the characteristics of NO formation in the bluff-body stabilized flames. The effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.3
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• pp.54-60
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• 2001

A newly designed inductive micro displacement detecting system is presented. The proposed inductive system consists of driving coils, position-detecting coils, cores, and closed-loop formed magnetic blocks. The cores and magnetic blocks are made of Mn-Zn ferrite. When AC sine wave is applied to the driving coils, the time derivative flux is generated within the system, and then induced voltages arise in the position-detecting coils according to the core\`s position. Putting the cores to be moved proportionally to the input displacement, the induced voltage is proportional to input displacement. The parameters that affect the system characteristics are turn ratio, air-gap size, excitation frequency, overlap area, load resistance, capacitance effect, and so forth. Based on the experimental results, the system parameters are selected in such a way as to have high sensitivity ad stable responses. The sensitivity of the proposed inductive displacement-detecting system is greater than 2800mV.V-1mm-1 and the linearity error is below $\pm$0.10% in the range of $\pm$200㎛.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.5
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• pp.110-117
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• 2002

This paper proposes a optimization of the design variables of linear motor for the improvement of thrust. Especially, this paper treats the shoe, which can be good to flow of a magnetic flux in linear motor. Firstly, this paper uses a space harmonic analysis method(SHAM) based on Fourier series, for analyzing the characteristics of core type linear motor, including slot structure and shoe. And compare the magnetic flux densities of linear motor at air gap with the results of the SHAM and the Finite Element Method(FEM). Secondly, this paper uses a genetic algorithm, which is good to find the global solutions. The design variables are the pole pitch of magnet, the pitch of slot, the height of slot, the width of shoe and the width of magnet. The maximum thrust with optimum design variables is about 247 N which is improved about 16%.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.3
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• pp.110-113
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• 2011

Platform Screen Door, PSD, is a device that seeks to prevent accidents with regards to falling off the platform and getting trapped between the trains, achieve improvements on the cleanliness of the air, address the accessibility issue of the disabled and the elderly and provide fresher environment on the platform in general. This is achieved by preventing health hazards and accidents from occurring through installation of fixed and moving doors between rail, tram and subway platforms and the railway. Domestic firms have achieved domestic production to a large degree in various Control Units including the Overall Control Unit and RF devices through investments in technology. Despite this, full domestic production of the core of the PSD system, Door Control Unit, DCU, is not yet achieved, having to install PSDs in a relatively short period of time. Currently, controllers with DC motors are developed for installation or one is faced with having to import foreign produced controllers. In this research, the control unit prototype using the BLDC motor was domestically produced. The performance of the control unit was rigorously tested through installation on Eun-Ha Rail on Wol-Mi Island.