• The Journal of Korean Medicine
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• v.29 no.2
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• pp.1-6
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• 2008

Objectives: This study aimed to investigate the seasonal variation in stroke types, ischemic stroke subtypes, stroke risk factors and Sasang constitutions. Methods: 226 patients with acute stroke within 14 days onset were included, who were admitted to Kyunghee Oriental Medical Center from November 2005 to October 2006. The year was subdivided into four parts: spring (March-May); summer (June-August); fall (September-November); and winter (December-February). Stroke types, ischemic stroke subtypes, stroke risk factors and Sasang constitutions in the four groups were examined. Results: Ischemic stroke was most frequent in summer, whereas hemorrhagic stroke was most frequent in winter. There was no significant difference in seasonal variation of stroke. The frequency of ischemic heart disease among stroke risk factors was significantly high in spring (p=0.031). The frequency of hypertension, diabetes mellitus, atrial fibrillation, and hyperlipidemia did not differ among seasons. There was no significant difference in Sasang constitution among seasons. Frequency of small vessel occlusion was highest in summer. Large artery atherosclerosis was frequent in spring and summer,but seasonal variation of ischemic stroke subtypes did not show statistical difference. Conclusion: Acute stroke demonstrates seasonal characteristics according to stroke types, ischemic stroke subtypes, risk factors for stroke, and Sasang constitutions. These results have important clinical implications in stroke prevention.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.3
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• pp.189-195
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• 2004

The underwater sound of California gary whale was analyzed to discuss obtained results from the previous data to compare the underwater sound between Korean gray whale and California gray whale. The frequency of low frequency rumble which occupy about 50% of the underwater sound changed to max. 654Hz and the average of its lasted time was 570msec. The range of frequency variation was coincided as compared with the previous data. The range of frequency variation for the bubble type sounds and knocks was 24${\sim}$1029Hz, respectively. The average of lasted time was 1100msec and 1364msec, respectively. The range of frequency variation and lasted time of bubble type sounds was higher than the previous result while the sound of knocks was coincided. The range of frequency variation for the sound of bong, pluses and chirps was 34${\sim}$213Hz, 75${\sim}$360Hz and 120${\sim}$200Hz, respectively and the average of lasted time was 84msec, 873msec and 80msec, respectively.

• Journal of electromagnetic engineering and science
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• v.12 no.1
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• pp.37-44
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• 2012

This paper describes a compact and novel wireless vital sign sensor at 2.4 GHz that can detect heartbeat and respiration signals. The oscillator circuit incorporates a planar resonator, which functions as a series feedback element as well as a near-field radiator. The periodic movement of a human body during aerobic exercise could cause an input impedance variation of the radiator within near-field range. This variation results in a corresponding change in the oscillation frequency and this change has been utilized for the sensing of human vital signs. In addition, a surface acoustic wave (SAW) filter and power detector have been used to increase the system sensitivity and to transform the frequency variation into a voltage waveform. The experimental results show that the proposed sensor placed 20 mm away from a human body can detect the vital signs very accurately.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.484-487
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• 2005

This paper presents an analytical approach to describe the variation in the vibration characteristics such as the natural frequency of a piezoelectric transducer under static pre-pressure. The transducer considered in this paper is a bolt clamped Langevin type transducer, which consists of a couple of piezoelectric discs, a couple of metal blocks for added mass effect, and a bolt to tighten them. A new analysis model for the transducer has been developed by taking into account the contact area between the piezoelectric ceramic and the metal block. The variation of the resonance frequency due to the pre-pressure has been calculated compared with other results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.2023-2032
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• 1993

This study suggests a new type shaft generating system driven by hydrostatic transmission suitable for small size vessels. Since the shaft generating system is affected ceaselessly by disturbances such as speed variation in pump driving speed and variation in external load, a robust servo control must be implemented to obtain stable electric power with constant frequency. Thus, in this study, a digital robust servo control algorithm is applied to the controller design. By the experiment and the numerical computation, the frequency variation characteristics of the generating system under various disturbances are investigated. Conclusively, it is said that the shaft generating system proposed in this study shows excellent control performances.

• The Korean Journal of Zoology
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• v.3 no.1
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• pp.13-18
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• 1960

1. Author has surveyed the frequency, geographic variation and micro-geographic variation of the elytral pattern types and the elytral edge of the population of lady-beetle, Harmonia axyridis Pallace which was collected in Seoul and the other 6 localities in Korea. 2. The number of specimen collected were 3.051 in which succinea occupied 88.32 % : Axyridis, 1.00% : spectabilis, 6.145 : and Conspicua , 4.545. 3. Of all 84.80% were found to have elytral edge. 4. There was a little difference in compositional proportation of the above four types to population and in the frequency of elytral edge between the population of west seaside and that of inland of Korea. 5. An interesting micro-geographic variation was observed in Dae-Chun, a beach located on west seaside of south Korea. In this locality , the Succinea occupied 45.23% and 27.805 were found to be provided with elytral edge in the specimen collected in pine trees ( Pinus thunbergii Parlatore), while in the specimen collected in burley field, oak, willow etc. 92.00% were Succinea and 90.93% were found to have elytral edge.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.90-94
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• 1998

The parallel inverter is popularly used because of its fault-tolerance capability, high-current outputs at constant voltages and system modularity. The conventional parallel inverter usually employes active and reactive power control or frequency and voltage droop control. However, these approaches have the disadvantages that the response time of parallel inverter control is slow against load and system parameter variation to calculate active, reactive power, frequency and voltage. This paper describes a novel control scheme for power equalization in parallel connected inverter. The proposed scheme has a fast power balance control response, a simplicity of implementation, and inherent peak current limiting capability since it employes a instantaneous current/voltage control with output voltage and current balance and output voltage regulation. A design procedure for the proposed parallel inverter controller is presented. Futhermore, the proposed control scheme is verified through the simulation in various cases such as the system parameter variation, the control parameter variation and the nonlinear load condition.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.176-181
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• 1998

The parallel inverter is popularly used because of its fault-tolerance capability, high-current outputs at constant voltages and system modularity. The conventional parallel inverter usually employs active and reactive power control of frequency and voltage droop control. However, these approaches have the disadvantages that the response time of parallel inverter control is slow against load and system parameter variation to calculate active, reactive power, frequency and voltage. This paper describes a novel control scheme for power equalization in parallel-connected inverter. The proposed scheme has a fast power balance control response, a simplicity of implementation, and inherent peak current limiting capability since it employees an instantaneous current/voltage control with output voltage and current balance and output voltage regulation. A design procedure for the proposed parallel inverter controller is presented. Furthermore, the proposed control scheme is verified through the experiment in various cases such as the system parameter variation, the control parameter variation and the nonlinear load condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.42-50
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• 1995

This paper proposes a new method to investigate combustion phenomena using the variation of crankshaft speed, From the idea that the variation of crankshaft speed contains the information of combustion, the energy method is applied as a single degree of freedom. Through the comparison of measured and calculated crankshaft speed, the proposed energy model is proved to be effective. When the crankshaft speed is used in the energy equation, filtering of the speed is required. The frequency components of cylinder pressure are analyzed and the coefficients of Fourier series above the twelfth frequency of engine speed are considered as a noise. As an example of application of this research, some combustion analyses like mean effective pressure, heat release rate, and misfire detection were carried out.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.583-584
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• 2006

This paper presents transistor matching in 70 nm nMOS. To adopt radio frequency(RF) applications, the RF performance, especially the current gain cutoff frequency($f_T$), is examined experimentally through a wafer. It is proved that the RF performance variation of 70 nm nMOS is dependent to the device geometry, the total width(W). The RF performance variation of 70 nm nMOS is inversely proportional to square root of total width(W). Also, decreasing of the number of fingers($N_f$) is helpful to decrease the variation of 70 nm nMOS.