• The Journal of Korean Physical Therapy
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• v.20 no.3
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• pp.45-51
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• 2008

Purpose: We evaluated the physical stress and pain to the musculoskeletal system of a dental practitioner when engaging in a dental scaling training exercise to prevent the development of musculoskeletal injuries. Methods: The 18 female (average age: 21$\pm$1 years) subjects were voluntarily picked from a group of juniors who have completed a one-and-a-half year training course that includes training exercises on the dentiform and on live subjects (other trainees). The test is done by measuring pain, activity, grip strength, and finger dexterity for each subject's hand and wrist. Before the test all subjects were confirmed to be right-handed and were informed of the study and its objective. Measuring was done before and after each subject performed dental scaling for one hour using the scaler and the curet. Results: Pain levels increased for both hand and shoulders, but hand pain was often greater than shoulder pain. Grip strength significantly declined in the right hand but not the left. For joint mobility, the flexion and the extension for the shoulder joint did not change; but the range of motion for both wrist joints significantly increased. For the dexterity test, both hands showed increased dexterity after the exercise. Conclusion: Dental scaling can affect the shoulders and wrists/hands. Therefore, a musculoskeletal injury prevention program for dental practitioners, which may include encouraging them to assume correct body posture when at work, must be sought. This study evaluated only the shoulders, wrists, and hands; but future studies should include areas such as the cervical area, the back, and the lower limbs.

• Polymer(Korea)
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• v.32 no.2
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• pp.169-177
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• 2008

The thermal and optical properties of cellulose tri(cholesteryloxy) carbonate(CCE0) and cellulose tri(cholesteryloxycarbonyl)alkanoates (CCEn, n=$2{\sim}8$, 10, the number of methylene units in the spacer) were investigated. CCE0 formed an enantiotropic cholesteric phase, whereas all the CCEn exhibited monotropic cholesteric phases. CCEn with n=$3{\sim}8$ formed cholesteric phases with left-handed helical structures whose optical pitches (${\lambda}_m's$) decrease with increasing temperature. On the other hand, CCE0 and CCEn with n=2 or 10 did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cholesteryl group highly depends on the length of the spacer connecting the cholesteryl group to the main chain. The thermal stability and degree of order in the mesophase and the temperature dependence of the ${\lambda}_m$ observed for CCEn highly depended on n. The results were discussed in terms of the differences in the internal plasticization, the arrangement of the side groups, and the conformation of the molecules.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.2
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• pp.85-89
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• 2011

In this paper, a novel Class-E power amplifier using metamaterials has been realized with one RF LDMOS diffusion metal-oxide-semiconductor field effect transistor. The CRLH structure can lead to metamaterial transmission line with the Class-E power amplifier tuning capability. The CRLH TL is achieved by the frequency offset and the nonlinear phase slope of the CRLH TL for the matching network of the power amplifier. Also, the proposed power amplifier has been realized by using the CRLH structure in the output matching network for better efficiency. Operating frequencies are chosen at 13.56 MHz in this work. The measured results show that the output power of 39.83 dBm and the gain of 11.83dB was obtained. At this point, we have obtained the power-added efficiency (PAE) of 73 % at operation frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.806-812
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• 2009

In this paper, the omnidirectional circularly polarized(CP) antenna using arc-shaped mushroom structure with curved branch is proposed. To obtain a vertical polarization and an omnidirectional radiation pattern, the CP antenna uses zeroth-order resonance(ZOR) mode of composite right and left handed(CRLH) transmission line. The horizontal polarization is achieved by the curved branches. Also, the spacing between curved branch and arc-shaped mushroom structure gives the $90^{\circ}$ phase difference between vortical and horizontal polarization. The proposed antenna, therefore, has an omnidirectional CP radiation pattern In the azimuthal plane. The electrical size of the proposed antenna is reduced by 38%, compared with that of the previously presented omnidirectional CP antenna. In addition, the CP antenna is simply designed without $90^{\circ}$ phase shifter and dual feed line. The proposed antenna uses a Bazooka balun for good impedance matching and radiation pattern. To improve 3 dB axial ratio in XY plane, the designed antenna is optimized. After optimization, the measured 3 dB axial ratio in XY plane is observed in $86{\sim}282^{\circ}$.

• Pediatric Infection and Vaccine
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• v.21 no.1
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• pp.59-64
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• 2014

The current paper reports on a case of subdural empyema secondary to frontal sinusitis in an otherwise healthy child. Sinusitis is a common and benign condition in most pediatric cases. Because of the widespread use of antibiotics, intracranial extension of pediatric sinusitis is rarely seen today; however, complications (e.g., cavernous sinus thrombosis, orbital infection, meningitis, and subdural empyema) are potentially life threatening. A 15-year-old right-handed male presented with a 3-day history of fever, headache, and left-sided palsy. Computed tomography revealed right-sided subdural empyema with right frontal sinusitis and maxillary sinusitis. A postoperative inpatient neurological consultation was requested 2 months post-surgery due to motor function deficits. The results suggested that early and accurate diagnosis of subdural empyema leads to prompt treatment and a favorable outcome for the patient.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.121-126
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• 2015

This paper proposes a novel reconfigurable microstrip antenna based on alternating a perturbation structure to achieve circular polarization diversity. The proposed antenna consists of an annular ring microstrip radiator for simultaneously loading stub and slot perturbations which support right- and left-handed circular polarization senses and two PIN diodes for choosing the operating polarization sense. By controlling the states of two PIN diodes between perturbing slot and stub at one diagonal corner of the radiator, reconfigurable circular polarization senses of the proposed antenna are successfully obtained and alternated. The proposed antenna has been theoretically analyzed and experimentally demonstrated at 2.4 GHz of S-band for satellite communication system. The simulation and measurement results of the proposed antenna show in good agreement with the reflection coefficients, axial-ratios, realized antenna gains, and radiation patterns.

• Journal of Advanced Navigation Technology
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• v.16 no.3
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• pp.433-439
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• 2012

In this paper, we proposed the triplexer using unit-cell of CRLH transmission line which has a bandpass characteristic to reduce adjacent channel interference. The input impedance of triplexer with each channel filter is operated open-circuit at the resonance frequencies of other channels. Such property is due to the combination a series and parallel resonance circuits of CRLH-TL unit-cell. The measured triplexer results are showed a measured insertion loss of each channel, less than 1.5 dB, matching at each port, less than 15dB and isolation between channel, better than 25 dB. Also, to validate the triplexer, a small signal amplifier with triple-band is designed and tested. the measured amplifier results show good agreements with prediction.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.143-151
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• 2010

In this paper, a novel rectangular patch antenna is proposed to have Zeroth Order Resonance(ZOR) generated based on the Metamaterial Complosite Right- and Left-Handed(CRLH) structure. Making the in-phase electric field over the entire antenna other than a half-wavelength as the fundamental resonance mode of a standard microstrip patch or its positive multiple, the metallic patch is suggested to be capacitively coupled with only one surrounding rectangular ring, different from the previous 1D ZOR antennas commonly having several metal cells in line. The performance of the proposed antenna is simulated by a 3D field solver that inputs the sizes of the physical structure corresponding to the equivalent circuit designed to have ZOR at 2.4 GHz. Consequently, the resonance frequency, the gain and the antenna efficiency are observed 2.4 GHz, 5 dB and 98%, respectively. Besides, the important property of the proposed antenna is addressed as the combination of the low profile as an advantage of microstrip patch antennas, and the omni-directional field pattern typical of monopole antennas.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.628-635
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• 1999

At center frequency of 11.85 GHz, wideband left-handed circularly polarized microstrip array antenna is designed with the method of sequential ratation based on $2\times2$ radiation elements($0^{\circ}$, $45^{\circ}$, $90^{\circ}$, $135^{\circ}$ phase delay). Its return loss, axial ratio bandwidth, radration pattern, and gain are compared with those adopting sequential rotation based on $1\times2$ radiation elements($0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$phase delay). The $8\times8$ array is manufactured and measured. The results show that 10 dB return loss bandwidth is 10.51~12.74GHz(18.82%) which is 1.57 times wider than the case using $1\times2$ sequential rotation method, 3 dB axial ratio bandwidth is 11.43~12.5 GHz(9.03%) which is 1.25 times as wide as that using $1\times2$ sequential rotation method and the antennal gain is 25.4 dB. The results of mesurements are almost similar to those of simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8C
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• pp.637-644
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• 2012

In this paper, a new compact power divider is suggested. Instead of the quarter wavelength transmission line(TX-line)s for the branches of the conventional Wilkinson's power divider design method, we use our composite right- and left-handed(CRLH) TX-line zeroth order resonator(ZOR) bandpass filters of one twelfth wavelength and reduce the physical length of the power divider. Besides, the filters in the branches can secure the passband for power-division. To validate the proposed power divider, we take an L-band for millitary satellaite transponder as the test case and the performances of the circuit and full-wave simulation results with the CRLH properties of the structure are shown with the dispersion curve and E-field at the ZOR. The measurement is compared with the simulation results. Also, the size reduction effect by the proposed scheme is addressed