• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.977-980
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• 1993

The technique to design high performance small motors has been based on experimental data, which results from lots of cost, experience and time in manufacturing. Recently, as high-performance computer appears, many engineers use numerical methods to design and analyze electric machine. Since, the step motor which has very small air gap(0.02-0.05mm) is different from other electric machine in its structure. The shape of rotor teeth and stator teeth influence seriously on the torque characteristics. And it is operated over magnetic saturation point. Therefore, the design of step motor needs to solve nonlinear problem and to calculate magnetic field precisely. In this paper, we solve nonlinear problem by employing Finite Element Method and obtain torque-displacement characteristics for the design of step motor. We also manufacture VR step motor according to the obtained results, and measure some torque characteristics. Through comparing calculated results with experimental results, it is verified that FEM is very useful to design step motor, and the motor designed by our technique is improved in its step accuracy.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.65-70
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• 2006

In the information storage development, the trend of the storage device is to increase the recording density. Among such an effort, near-field probe recording is spotlighted as a method of high increasing recording density. For the successfully embodiment of storage device, the actuating mechanism of near-field probe is essentially designed. In this paper, we suggest the slider similar with conventional HDD and design the slider using near-field probe for the purpose of applying the slider in order to control gap between probe and media. The most important object of slider design is to guarantee the flying ability and stability. For achievement of these design objects, we perform two step of optimal design process. The media is supposed to model as random displacement, which is only considered roughness of disk surface. The design slider is analyzed with dynamic state in assumed media. At this process, the optimal model is confirmed to stable flying stability.

• Journal of Ecology and Environment
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• v.47 no.4
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• pp.193-199
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• 2023

Background: The least weasel (Mustela nivalis) holds the distinction of being the world's smallest carnivorous animal, yet its presence in South Korea has remained poorly understood. To address this knowledge gap, this study investigates the habitat preferences and distribution of the least weasel in South Korea. Results: Our study compiled presence data from various sources, including citizen reports, national surveys, and expert observations. The results confirmed the nationwide presence of the least weasel in mainland South Korea, with notable concentration regions such as Gangwon province. Among the various habitats, forest edges and forests emerged as the predominant choice, with over half of the documented locations situated within these environments, particularly in broadleaf forests. Additionally, the data reveal a year-round presence of the least weasel, with recorded cases occurring at varying levels throughout the year. Conclusions: Our research advances the understanding of least weasels in South Korea. Despite the relatively modest dataset, our results provide as a valuable resource for future conservation initiatives, emphasizing the significance of forested landscapes. Additionally, it assists in identifying priority areas for protection and management efforts. To secure the future of the least weasel in South Korea and beyond, further research, including long-term monitoring and genetic studies, is imperative.

• Radiation Oncology Journal
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• v.26 no.3
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• pp.189-194
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• 2008

Purpose: We designed a water-based bolus device for radiation therapy in Kaposi's sarcoma. This study evaluated the usefulness of this new device and compared it with the currently used rice-based bolus. Materials and Methods: We fashioned a polystyrene box and cut a hole in order to insert patient's extremities while the patient was in the supine position. We used a vacuum-vinyl based polymer to reduce water leakage. Next, we eliminated air using a vacuum pump and a vacuum valve to reduce the air gap between the water and extremities in the vacuum-vinyl box. We performed CT scans to evaluate the density difference of the fabricated water-based bolus device when the device in which the rice-based bolus was placed directly, the rice-based bolus with polymer-vinyl packed rice, and the water were all put in. We analyzed the density change with the air gap volume using a planning system. In addition, we measured the homogeneity and dose in the low-extremities phantom, attached to six TLD, and wrapped film exposed in parallel-opposite fields with the LINAC under the same conditions as the set-up of the CT-simulator. Results: The density value of the rice-based bolus with the rice put in directly was 14% lower than that of the water-based bolus. Moreover, the value of the other experiments in the rice-based bolus with the polymer-vinyl packed rice showed an 18% reduction in density. The analysis of the EDR2 film revealed that the water-based bolus shows a more homogeneous dose plan, which was superior by $4{\sim}4.4%$ to the rice-base bolus. The mean TLD readings of the rice-based bolus, with the rice put directly into the polystyrene box had a 3.4% higher density value. Moreover, the density value in the case of the rice-based bolus with polymer-vinyl packed rice had a 4.3% higher reading compared to the water-based bolus. Conclusion: Our custom-made water-based bolus device increases the accuracy of the set-up by confirming the treatment field. It also improves the accuracy of the therapy owing to the reduction of the air gap using a vacuum pump and a vacuum valve. This set-up represents a promising alternative device for delivering a homogenous dose to the target volume.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.55 no.4
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• pp.327-332
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• 2010

This study was conducted to overcome the deliciousness by sex reversal in hemp plants. When female plants grown under long day length condition were transferred to short day length condition in 3th and 6th leaf stage, a few male flowers were formed and the gap of flowering days between sex reversed male and normal female flowers were around 10 days and 3 days, respectively. Although the flowering amounts were small, this short gaps of flowering days were enough for artificial pollination. When female plants grown under long day length condition were transferred to short day length condition just after treatment of silver nitrate in the vegetative stage, a great amount of male flower was formed and the gap of flowering days between sex reversed male and normal female flowers were only 1 to 3 days. The increased sex reversed male flowers and induced short gap of flowering days were adequate for natural wind pollination. When female seeds were cultivated, seed yield was 141 kg/10a, while it was 96 kg/10a when normal seeds cultivated.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.21 no.2
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• pp.121-127
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• 2010

Background and Objectives : Unilateral vocal fold paralysis is generally treated using injection laryngoplasty or voice therapy. However, the decision of treatment method is dependent on clinician's preference and hospital facilities without specific criteria. The purpose of the study was to examine factors predictive of voice therapy outcome in patients with unilateral vocal fold paralysis. Materials and Method : 38 patients diagnosed as unilateral vocal fold paralysis, aged from 24 to 81 years and undergone voice therapy more than 1 month were included. After 3 to 12 (mean 5.1) sessions of voice therapy, subjects had divided into responder group (RG, 28 patients) and non-responder group (NRG, 10 patients) according to G scale change. Paramters of perceptual assessment, acoustic and aerodynamic measure, and videostroboscopy were compared between two groups, and factors predictive of voice therapy result were analyzed. Results : RG patients showed significantly reduced rough, breathy, asthenic voice after voice therapy. Change of MPT and MFR was more substantial in RG than in NRG. By videostroboscopy, RG patients showed significantly more mucosal wave symmetry, glottal closure, reduced glottal gap index during the closed phase of phonation, while NRG patients showed more occurrences of abnomal supraglottic activities during phonation (p < 0.05). Poor outcome of voice therapy significantly associated with increased asthenic scale, short MPT, and less glottal closure (p=0.02). In addition, 90% of patients with MPT more than 5 seconds were in RG, whereas 56% of patients with MPT less than 5 secondes were in RG. Conclusion : Voice therapy is useful for large proportion of patients with unilateral vocal fold paralysis as an initial treatment method. However, patients with large asthenia scale, large glottic gap or MPT less than 5 seconds tend to have poor voice therapy outcome, and early injection laryngoplasty maybe recommended for these patients.

• Current Applied Physics
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• v.18 no.11
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• pp.1306-1312
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• 2018

The Mn-doped copper nitride ($Cu_3N$) films with Mn concentration of 2.0 at. % have high crystallinity and uniform surface morphology. We found that the as-synthesized Mn-doped $Cu_3N$ films show suitable optical absorption in the visible region and the band gap is ~1.48 eV. A simple photodetector based on Mn doped $Cu_3N$ films was firstly fabricated via magnetron sputtering method. The fabricated device with doping of Mn demonstrated high photocurrent response and fast response shorter than 0.1 s both for rise and decay time superior to the pure $Cu_3N$. Furthermore, the energy levels of Mn-doped Cu3N matched well with ITO and Ag electrode. The excellent photoelectric properties reflect a good balance between sensitivities and response rate. Our investigation reveals the excellent potential of Mn-doped $Cu_3N$ films for application of photodetectors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.429-432
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• 2008

Much studies have been concentrated to develop the fabrication technique for high critical current density but still there are a lot of gap which should be overcome for large scale application of superconducting materials at liquid nitrogen temperature. The improvement of the critical current can be achieved by forming the nano size defect working as a flux pinning center inside the superconductor. In this paper, the establishment of fabrication condition and additive effects of second elements were examined so as to improve the related properties to the practical use of superconductor.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2008.03a
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• pp.122-122
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• 2008

• Journal of electromagnetic engineering and science
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• v.5 no.4
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• pp.204-207
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• 2005

In this paper, PBG structure and feedforward circuit has been used to suppress the phase noise of the oscillator. Microstrip line resonator have low Q, but we can obtain high LO power by feedforward circuit and improve the resonator Q by the PBG, simultaneously. The proposed oscillator which uses PBG and feedforward circuit shows 0${\~}$20 dB phase noise reduction compared to the conventional oscillator. We have obtained -115.8 dBc of phase noise at 100 kHz offset from 2.4 GHz center.