• Progress in Superconductivity and Cryogenics
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• v.22 no.2
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• pp.38-43
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• 2020

This paper presents comparative research on characteristics of air-cored and iron-cored high-temperature superconductor (HTS) field winding synchronous motors. The 100 kW air-cored model is designed analytically by Spatial Harmonic Method, and based on this model, the iron-cored model having the same output power is designed for comparison. Due to the substantial difference of permeability property between air and iron-core, there is a difference of magnetic field magnitude and angle with respect to the HTS tape c-axis, resulting in a different critical current of the field winding considering the anisotropic property of HTS tape. For a detailed comparison between two models, the following key motor characteristics are calculated through the Finite Element Method (FEM) simulation: 1) critical current; 2) HTS wire length; and 3) torque characteristics. From the simulation results, it can be confirmed that the critical current value of the iron-cored model increases by 33 %. Also, in the case of the superconducting wire consumption, those of the iron-cored and air-cored models are 95.3 m and 815.6 m, respectively. So the wire usage can be reduced to about 88 % by using iron core. However, in terms of torque characteristics, the torque ripple of the iron-cored model is about twice as large as that of the air-cored model, which may be a disadvantage on vibration and acoustic noise.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.393-400
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• 2014

In this paper, we have designed the transmitter for earth station terminal operating with military geostationary satellite on Ka-band that is complied with MIL-STD-188-164A. The designed antenna of this terminal is dual-offset gregorian reflector which is consist of corrugated horn and iris polarizer, othermode transducer. This antenna meets radiation pattern and transmit EIRP spectral density requirements in this standard. The designed RF systems of this terminal are consist of Block Up Converter(BUC) converting frequency band from IF to Ka band and SSPA having low-power consumption and compact light-weight using the pHEMT MMIC compound devices. This RF systems applied with VSWR, spurious/harmonic suppression, output flatness and phase noise requirement in this standard.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.4
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• pp.28-34
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• 2000

In this paper, a continuous-time filter for low voltage and high frequency applications using fully-balanced current integrators is presented. As the balanced structure of integrator circuits, the designed filter has improved noise characteristics and wide dynamic range since even-order harmonics are cancelled and the input signal range is doubled. Using complementary current mirrors, bias circuits are simplified and the cutoff frequency of filters can be controlled easily by a single DC bias current. As a design example, the 3rd-order lowpass Butterworth filter with a leapfrog realization is designed. The designed fully-balanced current-mode filter is simulated and examined by SPICE using 0.65${\mu}{\textrm}{m}$ CMOS n-well process parameters. The simulation results show 50MHz cutoff frequency, 69㏈ dynamic range with 1% total harmonic distortion(THD), and 4㎽ power dissipation with a 3V supply voltage.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.11 no.1
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• pp.46-50
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• 2000

Background and Objectives : Hormonal treatments which have an androgenic effect have the potential to cause vocal changes. The changes in vocal fold structure and voice quality are considered to be irreversible. To date, studies have documeted subjective vocal changes or documented single cases without detailed, baseline voice assessments. Materials and Methods : We have performed objective voice analyses of 20 women who were treated with androgenic hormones for endometriosis and compared the results with those of normal control women. Results : The averages of fundamental frequency were 194.7${\pm}$28.2 in study group, 207.0${\pm}$14.1 in control group. The means of closed quotient which were measured with electroglottography were 45.13${\pm}$2.06 in study group, 45.1${\pm}$3.03 in control group. Results of acoustic analysis are as follows. The averages of jitter were 0.95${\pm}$0.46 in study group, 1.10${\pm}$0.65 in control group. The means of shimmer were 2.44${\pm}$0.60 in study group, 2.32${\pm}$1.09 in control group. The averages of noise to harmonic ratio were 0.13${\pm}$0.028 in study group, 0.15$\pm$0.18 in control group. Conclusion : Although there were no statistically meaningful differences between the two groups, we could detect the masculinizing tendency of the therapeutic hormones of endomentriosiss(lowering of fundamental frequency). Given the availability of objective voice assessments today and the continued use of these potent hormones, comprehensive voice assessment and vocal monitoring would appear vital for women commencing hormonal treatment.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.29 no.1
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• pp.37-40
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• 2018

Background and Objectives : This study aimed to evaluate patients' subjective and objective outcomes after laryngeal microsurgery for benign vocal fold (VF) lesions, and to identify usefulness of surgical treatment. Materials and Methods : The authors reviewed the 102 patients medical records, retrospectively who received laryngeal microsurgery for benign VF lesions from January 2013 to August 2017. Subjective voice were measured using the Voice Handicap Index (VHI). Objective voice were recorded with Multi-Dimensional Voice Program (MDVP) just before surgery, and after at least 3 months of surgery. Results : Benign VF lesions were categorized as VF nodule (n=34, 33%), VF Polyp (n=47, 26%), Intracordal cyst (n=15, 15%), Reinke's edema (n=6, 6%), and VF Papilloma (n=2, 2%). Post-operative voice assessment at VHI scores showed statistically significant reductions in all of functional, physical and emotional parts (p<0.001). MDVP were showed significant improvement of Jitter (P=0.001), Shimmer (p<0.001) and Noise to Harmonic Ratio (NHR) (p=0.001). Conclusion : Laryngeal microsurgery for benign vocal fold lesions is effective treatment with statistically significant improvement at subjective and objective vocal quality assessment.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.2
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• pp.154-162
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• 2007

In this paper, we propose a new AC-DC converter control method to comply with harmonics regulation(IEC 61000-3) effective for the inverter system of an air conditioner whose power consumption is less than 2,500W. There are many different ways of AC-DC converter control, but this paper focuses on the converter control method that is adopting an input reactor with low cost silicon steel core to strengthen cost competitiveness of the manufacturer. The proposed control method controls input current every half cycle of the line frequency to get unit power factor and at the same time to reduce switching loss of devices and acoustic noise from reactor. This kind of converter is known as a Partial Switching Converter(PSC). In this study, theoretical analysis of the PSC has been performed using Matlab/Simulink while a 16-bit micro-processor based converter has been used to perform the experimental analysis. In the theoretical analysis, electrical circuit models and equations of the PSC are derived and simulated. In the experiments, micro-processor controls input current to keep the power factor above 0.95 by reducing the phase difference between input voltage and current and at the same time to maintain a reference DC-link voltage against voltage drop which depends on DC-link load. Therefore it becomes possible to comply with harmonic regulations while the power factor is maximized by optimizing the time of current flow through the input reactor for every half cycle of line frequency.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.24 no.2
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• pp.112-117
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• 2013

Background and Objectives : This study aimed to determine the clinical effect of $Artecoll^{(R)}$ injection laryngoplasty for patients with vocal atrophy and mild sulcus vocalis. Materials and Method : Forty-one patients with vocal atrophy and/or mild sulcus vocalis received transcutaneous $Artecoll^{(R)}$ injection into the vocal folds under local anesthesia. Subjective evaluations including voice handicap index (VHI) and perceptual grading with Grade, Roughness, Breathiness, Asthenia, Strain (GRBAS) scales and objective evaluations including jitter, shimmer, noise-to-harmonic ratio (NHR), speaking fundamental frequency (SFF) and maximum phonation time (MPT) were evaluated before and 3 months after the injection. Results : VHI and Grade, Breathiness and Strain scales in GRBAS showed significant improvement 3 months after injection. SFF and MPT also significantly improved after the injection ; MPT increased and SFF in male patients decreased. Conclusion : Injection laryngoplasty with $Artecoll^{(R)}$ is an effective method for correcting the glottal insufficiency and improving voice quality in patients with vocal atrophy and/or mild sulcus.

• Speech Sciences
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• v.15 no.2
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• pp.131-141
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• 2008

The purpose of this study was to find out the acoustic variation on the pre-and post respiration and oral motor for children with cerebral palsy. Five children with spastic CP at the age of 6 in average were practiced by a caregiver at home each for 25 minutes, in total, 45 times. The sustained of vowel /a/ and vowels /a/, /i/, /u/, /e/, /o/ were recorded on CSL and MDVP and analyzed by acoustic parameters. As a result, the maximum phonation time(MPT) was increased from 2.06 to 6.31 and the formant of vowels(F1, F2, F3) had significant differences in F1(/a, i/), F2(/i.u.o/), and F3(/a/) between the controls and the children with CP in pre-treatment. The total average value of vowels had significant differences between the pre-and post-treatment (p< .05). The energy of vowels had significant differences in the vowels /i, u, e, o/ and the total average value between the pre-and post-treatment(p< .001). The jitter percent, shimmer percent, and noise to harmonic ratio had significant differences between the pre-and post-treatment(p< .05). As the respiration and the oral motor improved MPT, voice quality, and articulation of vowel, and the variation of the formant(F1, F2, F3) showed the changes in the shape of lips, the place and the height of the tongue, the various development of therapy programs and the consistent intervention of treatment is needed for the children with cerebral palsy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.833-842
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• 1998

In this paper, a K-band oscillator which is composed of a hair-pin resonator, a GaAs MESFET, and a frequency doubler, is suggested, implemented by HMIC(Hybrid Microwave Integrated Circuits) form, and characterized for its microwave performance. A $\lambda_g$/4 open stub is used in frequency doubler to suppress the fundamental frequency of 9 GHz which is the output of the hair-pin resonator oscillator and output matching network is optimized for its second harmonic freuency of 18 HGz. For the oscillator, the output power of -0.83 dBm, the fundamental frequency suppression of -23 dBc, and phase noise of -86 dBc/Hz at 18.20 GHz are obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.923-929
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• 2017

Generally, the sound emitted from a vehicle powered by an electric motor is lower than that of internal combustion engine vehicles. Therefore, pedestrians often cannot detect approaching electric vehicles. Therefore, a certain additional warning sound is required for these types of automobiles. In this study, to develop an audible warning sound, nine warning sounds are designed based on signal processing and chord theory. The background noise measured on the road is also added to these synthetic sounds. The detectability of these warning sounds is evaluated by subjective tests. The sound metric is correlated to detectability and is investigated through psychoacoustic theory and subjective evaluation. It is determined that known psychoacoustic parameters such as loudness, sharpness, and roughness have a low correlation with detectability. However, it is found that the interval of harmonic sound correlates well with detectability.