• Journal of the Ergonomics Society of Korea
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• v.32 no.5
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• pp.413-420
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• 2013

Objective: The objective of this study was to compare one-hand and two-hands lowering activity in terms of biomechanical stress for the range of lowering heights from knuckle height to 10cm above floor level. Background: Even though two-hands lifting/lowering activity of manual materials handling tasks are prevalent at the industrial site, many manual materials handling tasks which require the worker to perform one-hand lifting/lowering are also very common at the industrial site and forestry and farming. Method: Eight male subjects were asked to perform lowering tasks using both a one-handed as well as a two-handed lowering technique. Trunk muscle electromyographic activity was recorded while the subjects performed the lowering tasks. This information was used as input to an EMG-assisted free-dynamic biomechanical model that predicted spinal loading in three dimensions. Results: It was shown that for the left-hand lowering tasks, the values of moment, lateral shear force, A-P shear force, and compressive force were increased by the average 6%, as the workload was increased twice from 7.5kg to 15kg. For the right-hand lowering task, these were increased by the average 17%. For the two-hands lowering tasks, these were increased by the average 14%. Conclusion: Even though the effect of workload on the biomechanical stress for both one-hand and two-hands lowering tasks is not so significant for the workload less than 15kg, it can be claimed that the biomechanical stress for one-hand lowering is greater than for two-hands lowering tasks. Therefore, it can be concluded that asymmetrical lowering posture would give greater influence on the biomechanical stress than the workload effect for one-hand lowering activity. Application: The result of this study may be used to provide guidelines of recommended safe weights for tasks involved in one-hand lowering activity.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.1
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• pp.183-192
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• 2005

This study compared cerebral lateralization index based on the area of neural activation with that based on the intensity of neural activation. For this purpose, 8 right-handed male college students (the mean age - 23.5 years) and 10 right-handed male college students (the mean age - 25.1 years) participated respectively in researches on visuospatial and verbal task brain function. Functional brain images were taken from 3T MRI using the single-shot EPI method. The result of measuring cerebral lateralization index based on the area of neural activation suggested that the right hemisphere is dominant in visuospatial tasks and the left one is in verbal tasks. However, the dominance is not sufficient to locate the exact part of the brain for these tasks. When cerebral lateralization index was computed based on the intensity of neural activation, it was derived that the area of cerebral lateralization closely related to visuospatial tasks is the superior parietal lobe, and the area of cerebral lateralization closely related to verbal tasks is the inferior and middle frontal lobes. Thus, cerebral lateralization index by area based on the intensity of neural activation as proposed by this study can determine the dominance of the cerebrum by area, so is helpful for accurate and quantitative determination of cerebral lateralization.

• Polymer(Korea)
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• v.28 no.1
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• pp.92-102
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• 2004

(6-Cholesteryloxycarbonylpentoxypropyl)celluloses (CHPCs) with degree of esterification (DE) ranging from 2.25 to 2.91 were synthesized by reacting hydroxypropyl cellulose with 6-cholesteryloxycarbonylpentanoyl chloride. The acrylic esters of CHPCs (CHPCEs) and their photocrosslinked films with liquidcrystalline order were also synthesized. The thermotropic properties of mesophase for both uncrosslinked and crosslinked samples and the swelling behavior of the crosslinked samples in acetone were investigated. The hydroxypropyl cellulose exhibited an enantiotropic cholesteric phas, while all the uncrosslinked cholesterylbearing samples exhibited a monotropic cholesteric phases; the 6-cholesteryloxycarbonylpentanoyl chloride also showed a monotropic smectic phase. The hydroxypropyl cellulose formed a right-handed helix whose optical pitch (λ$\sub$m/) increases with temperature, whereas all the uncrosslinked derivatives farmed left-handed helices whose λ$\sub$m/'s decreased with temperature. The thermal stability of the mesophase and the magnitude of λ$\sub$m/ at the same temperature for both CHPCs and CHPCEs decreased with increasing DE. All the crosslinked samples, in constrast with CHPCEs, did not display reflection colors but exhibited an anisotropic swelling characteristic of crosslinked gel retaining liquid-crystalline order.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.1
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• pp.46-52
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• 2010

A compact circular microstrip patch antenna with a switchable circular polarization(CP) is proposed at 2.4 GHz. An unequal cross-shaped slot on a ground plane is utilized as a perturbation. By switching pin diodes mounted on the slot, the CP sense of each antenna can be simply switched from left-handed(LH) CP to right-handed(RH) CP vice versa. Since the perturbation can be made on the ground plane and no bias circuit is required on the patch side, the bias circuit has not effect on the main beam radiation. From the experimental results, the impedance bandwidth and CP bandwidth of the proposed antenna have shown up to 150 MHz and 35 MHz, respectively. The peak gain of the proposed antenna is 1.7 dBi for both CP senses.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.10
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• pp.1084-1090
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• 2009

This paper presents a balun consisting of a T-junction, a Right/Left Handed Transmission line(RLH-TL), and a conventional Right Handed(RH) line. It is assumed that the RLH-TL consists of N unit-cells. We provide closed-form solutions and design a very compact wideband(80 %) balun using CPW lines based on the obtained solutions. Then, we propose a capacitively loaded loop antenna designed for a uniform current distribution. The antenna resistance of the proposed antenna at resonance is about 204 ohms. The length of the unit cell is about $\lambda/12$(total length: $1\;\lambda$). The magnetic field generated from the proposed antenna is stronger than that of the conventional one by as much as 20 dB. We used a coplanar strip line(CPS) to combine the loop antenna and balun. The proposed antenna may be used as a near field UHF RFID reader antenna.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.72-81
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• 2014

Even though two-hands lifting/lowering activity of manual materials handling tasks are prevalent at the industrial site, many manual materials handling tasks which require the worker to perform one-hand lifting/lowering are also very common at the industrial site, forestry, farming, and daily life. The objective of this study was to compare one-hand lowering activity to lifting activity in terms of biomechanical stress for the range of lowering heights from knuckle height to 10cm above floor level with two workload 7.5kg and 15.0kg. Eight male subjects with LMM were asked to perform lifting/lowering tasks using both a one-handed (left-hand and right-hand) as well as a two-handed technique. Spinal loading was estimated through an EMG-assisted free-dynamic biomechanical model. The biomechanical stress of one-hand lowering activity was shown to be 43% lower than that of one-hand lifting activity. It was claimed that the biomechanical stress for one-hand lifting/lowering activity is almost twice (194%) of the one for two-hands lifting/lowering activity. It was also found that biomechanical stress by one-hand lowering/lifting activity with the half workload of two-hands lowering/lifting activity was greater than that of the two-hands lowering/lifting activity. Therefore, it might be a risk to consider the RWL of one-hand lowering/lifting activity to simply be a half of the RWL of two-hands lowering/lifting activity recommended by NIOSH.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.2
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• pp.113-121
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• 2013

In this paper, quadruple polarized antenna system with a reconfigurable feeding network is presented. The proposed antenna system consists of the reconfigurable feeding network for fourth polarization such as vertical/horizontal linear polarization and right-handed/left-handed circular polarizations or 45 degree tilted vertical/horizontal linear polarization and patch antenna to receive the signals with various polarizations. In order to receive a signal in any direction, the proposed antenna is designed by electrical switches for reconfigurable polarization. The insertion loss of the designed feeding network in the proposed antenna system is approximately 1.2 dB. The measured 3 dB axial bandwidth and gain of the proposed antenna are about 2 % and 4 dBi(c).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.73-77
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• 2012

In this article, we designed a wide bandpass filter in order to apply microwave reflectometry for KSTAR. The proposed wide bandpass filter consists of a metamaterial structure which is to get a wide band, a lower insertion loss, and a high skirt. This is applied to VCO's output to enhance the linearity. A pass band is 18-28 GHz and the out of pass band is stopped over 20 dB. To confirm of the metamaterial, we suggest a dispersion diagram. The proposed filter in lower band and upper band of pass band is respectively a left handed and right handed characteristics. A group delay is below 0.5 ns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.837-843
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• 2008

This paper proposes a power divider based on meta-material structure with dual-band operation. The meta-material structures of left-hand characteristic are constituted of series capacitors and shunt inductors, but they have parasitic series inductance and shunt capacitance effects. There is represented the composite right/ left-handed transmission line (CRLH-TL) model. When the power divider is implemented by using the CRLH-TL, the power divider can operate dual band. To verify the power divider with dual band, we are implemented to operate dual-band that is 0.88 GHz and 1.67 GHz. The characteristics of divider have the return loss less than each 21.0 dB and 15.8 dB and the insertion loss better than 3.83 dB and 3.64 dB at each frequency. Also, the output phase difference is $3{\sim}6^{\circ}$.

• Physical Therapy Korea
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• v.25 no.3
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• pp.51-59
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• 2018

Background: Despite muscle latency times and patterns were used as broad examination tools to diagnose disease and recovery, previous studies have not compared the dominant arm to the non-dominant arm in muscle latency time and muscle recruitment patterns during reaching and reach-to-grasp movements. Objects: The present study aimed to investigate dominant and non-dominant hand differences in muscle latency time and recruitment pattern during reaching and reach-to-grasp movements. In addition, by manipulating the speed of movement, we examined the effect of movement speed on neuromuscular control of both right and left hands. Methods: A total of 28 right-handed (measured by Edinburgh Handedness Inventory) healthy subjects were recruited. We recorded surface electromyography muscle latency time and muscle recruitment patterns of four upper extremity muscles (i.e., anterior deltoid, triceps brachii, flexor digitorum superficialis, and extensor digitorum) from each left and right arm. Mixed-effect linear regression was used to detect differences between hands, reaching and reach-to-grasp, and the fast and preferred speed conditions. Results: There were no significant differences in muscle latency time between dominant and non-dominant hands or reaching and reach-to-grasp tasks (p>.05). However, there was a significantly longer muscle latency time in the preferred speed condition than the fast speed condition on both reaching and reach-to-grasp tasks (p<.05). Conclusion: These findings showed similar muscle latency time and muscle activation patterns with respect to movement speeds and tasks. Our findings hope to provide normative muscle physiology data for both right and left hands, thus aiding the understanding of the abnormal movements from patients and to develop appropriate rehabilitation strategies specific to dominant and non-dominant hands.