• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.349-352
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• 2008

Thrust vectoring control by injection of secondary jet inside a convergent-divergent supersonic nozzle was studied by both experimentally and computationally. For various stagnation pressure of the secondary jet injected at a specific location(12 mm-downstream of throat) in the divergent section of nozzle, the characteristics of thrust vectoring were observed. Present numerical results were compared with previous investigators' results and Schlieren flow visualizations for the identical boundary conditions, and it showed a qualitatively good agreement. It was also noticed that the characteristics of thrust vectoring is strongly related to the reflection structure of oblique shock inside nozzle, ie., the pressure ratio of the secondary jet, SPR.

• Journal of Clinical Otolaryngology Head and Neck Surgery
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• v.29 no.2
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• pp.190-197
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• 2018

Background and Objectives : Positional OSAS is characterized by an apnea-hypopnea index (AHI) score >5, which, while sleeping in the supine position, is double that in non-supine position. This study was performed to compare the clinical characteristics of positional OSAS and non-positional OSAS patients, and the effects of the modified jaw thrust maneuver during drug-induced sleep endoscopy (DISE) between positional OSAS and non-positional OSAS patients. Materials and Methods : 68 positional OSAS patients and 19 non-positional OSAS patients were included. They all underwent full-night polysomnography and DISE. The modified jaw thrust maneuver was introduced during DISE. Airway structural changes induced by the modified jaw thrust maneuver were evaluated and documented. Results : There were no statistically significant differences in Friedman stage or tonsil grade, body mass index, Epworth sleepiness scale (ESS) score, blood pressure, AHI, or obstructive pattern between the positional and non-positional OSAS patients. However, mean arterial oxygen saturation (SaO2), lowest SaO2, and total arousal index values were more severe in the non-positional OSAS patients. After introduction of the modified jaw thrust maneuver, retrolingual level obstruction showed a tendency toward a higher rate of airway opening in positional OSAS patients than in non-positional OSAS patients. Conclusions : The effects of a mandibular advancement device (MAD) can be estimated by carrying out a modified jaw thrust maneuver during DISE. The tendency toward a higher rate of airway opening in positional OSAS patients than non-positional OSAS patients in retrolingual level obstruction after jaw thrust maneuver introduced during DISE may be clinically important for MAD.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.4
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• pp.394-398
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• 2013

This paper presents output characteristics of a linear switched reluctance motor (LSRM) with excitation windings wound by using high-temperature superconducting (HTS) tapes. In a double-sided LSRM, Bi-2223 or YBCO tape conductors are used for the excitation windings. The characteristics of the LSRM are obtained by a finite element method analysis. We can obtain large thrust compared with a conventional LSRM by using YBCO tape conductors. Also, the effect of a configuration of the YBCO coil on the thrust is calculated. We discuss a suitable coil configuration for the average thrust upgrading.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.453-456
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• 2001

The thrust control characteristics of single-sided linear induction motor (SLIM) is achieved using PI controller in this paper. The trembling of air gap length between the primary winding and the secondary structure of the SLIM must be minimized in order to get quick response results. Also, the input voltage of SLIM is involved with the time harmonics because most SLIM is driven by inverter. According to the feedback linear control system, this paper describes with applying the non-linear control, speed and estimated flux algorithm. At the result of this experiment, we reached to the improvement of thrust characteristics with PI controller.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.255-264
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• 2002

In this paper, the power transmitting mechanism for negative torque of the metal V-belt (MVB) CVT were investigated by theoretically analyzing variation of band tension, block compression forces for each of the primary and secondary pulleys. An experimental study was performed to investigate the speed ratio - thrust characteristics for negative torque. The experimental results are in good acoordance with the theoretical results. CVT line pressure control logic was suggested for negative torque based the speed radio - negative torque - thrust characteristics and the thrust ratio curves. The results of this study can be used as basic design materials for developing the CVT control system for negative torque.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.750-755
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• 2011

The ignition characteristics of liquid rocket engine thrust chambers which have been developed by domestic technology were analyzed. Analysis results showed that low frequency fluctuation appeared in a partial ignition range according to different temperature profiles and vaporous state in the oxidizer manifold with startup sequences. This low frequency fluctuation wasn't developed as a malfunction factor, but this fluctuation is thought to be taken a continuous concern considering interfaces with engine system and launch vehicle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.662-665
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• 2011

Pintle technology, which is one of the thrust control method for solid rocket motor, can control the thrust by the control of nozzle throat area through the pintle moving. For studying the unsteady flow characteristics of pintle nozzle by needle type pintle moving, cold flow test and numerical analysis were performed. The pressure distribution on the pintle tip was varied for pintle moving and stopping and thrust was varied by this effects.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.639-646
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• 2002

In this paper, thrust equations for a rubber belt CVT are derived by considering the geometry and mechanism of the mechanical actuators. In order to solve the thrust equations, an algorithm to calculate the speed ratio is suggested for the given driver speed and load torque based on the actuator characteristic equations and existing formula for the belt thrust forces. Experiments are performed to investigate the driver speed-load torque-speed ratio characteristics at a steady state. The speed and torque efficiencies are measured and used to modify the actuator equations. It is found that the modified equations well predict the steady state characteristics. In addition, the shift dynamic model for a rubber belt CVT is derived experimentally. Simulation results of the CVT shift dynamics are in good accordance with the experiments and it is noted that different coefficients are required to describe the CVT shift dynamics for the upshift and the downshift.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.643-644
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• 2008

This paper is analyzed the effect on characteristics of thrust force of linear induction motor(LIM) by rotational type tester. Many kinds of tester have a rotational shape because of a finite length of railroad. Whereas effects by using rotational type tester are generally unknown. For reason of that, this paper will be analyzed the effect on characteristics by rotational type tester using 2D finite element method(FEM), and then will be compared a thrust force between linear type tester and rotational type tester.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1661-1666
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• 2009

This paper is analyzed the effect on characteristics of thrust force of linear induction motor(LIM) by arc type tester. Many kinds of tester have a rotational shape because of a finite length of railroad. Whereas effects by using rotational type tester are generally unknown. For reason of that, this paper is analyzed the effect on characteristics by rotational type tester using 2D finite element method(FEM), and then is compared a thrust force between linear type tester and rotational type tester. Analysis model is decided by numerical modeling for fitting the LIM for propulsion system of light rail, and it is changed to proper arc model. And then we analyzed the arc and the linear model. Consequently, arc type tester is not only useful experiment but also efficient simulation method, and small error is occurred between linear and arc model.