• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.318-321
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• 1997

This paper is about improving characteristic of plant by using micro-step driver method in 5 phase step motor for satisfying the condition of low oscillation and high accuracy in soldering machine. We choose open loop control method for minimizing hardware system and use one chip microprocessor, power MOSFET nd some device to realize accurate micro-step driver system.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.202-203
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• 2007

STATCOM은 계통에 무효 전력을 공급함으로써 모선 전압을 유지시키는 역할을 한다. 따라서 발전기들의 회전자 위상각과 같은 유효전력과 관련된 계통 변수들의 제어 능력은 없다. 그러나 여자기에 PSS와 같은 제어기를 설치하여 발전기 회전자 진동을 제어하는 것처럼 STATCOM에도 이러한 제어기를 설치함으로써 부가적인 효과를 얻을 수 있다.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2505-2507
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• 1999

This paper presents novel self excited DC-DC converters such as Buck-boost type, Buck type and also non-inverting Buck-boost type. The proposed converters has the following advantages: simple topology, small number of circuit components, easy control methode. Therefore, these converters are suitable for the portable appliances with battery source. Theoretical analysis and experimental results for SOW class Buck-boost type self oscillation DC-DC converter have been obtained, which demonstrate the high efficiency and good performance.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.127-132
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• 2003

Through advance in construction techniques, engineering progress, availability of new materials, and economic considerations, buildings are becoming taller, lighter, and more flexible. In addition, today/s buildings are largely of regular geometric shape with smooth glass metal exteriors, which increase the likelihood of vortex shedding. The wind induced oscillation of the building, if not properly damped, could cause occupant discomfort and other problem. This paper will deal with residual building structure equipped with viscoelastic dampers. And the dampers are installed on the 42th story according to the maximum relative deformation.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.499-501
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• 1995

In this paper, the generation of the intensive ultrasonic waves depend mainly on the energy convention efficiency depending on high frequency oscillation of the generator and the control performance of stable output depending on iode variation. As a result, the ultrasonic generator obtained of 95% differency with 28khz.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1901-1905
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• 2004

A controller designed by CDM for a servo type system which is an augmented system constructed from a rotational inverted pendulum with an integrator added to its arm, is presented in this paper. In order to be able to apply the CDM concept, the augmented system must be linearized and converted into controllable canonical form. Then, the controller consisting of the state feedback gain matrix and an integral gain in the sense of CDM can be obtained. This shows that design procedure for the proposed controller is easy. The experimental results obtained from the rotational inverted pendulum controlled by the proposed controller show that the system response has no steady-state error, however, the oscillation amplitude of the arm angle is still significant. Therefore, in this paper, the friction compensation using Coulomb friction with stiction is also added to the controller. The oscillation amplitude of the arm angle that can be reduced remarkably is also shown in the experimental results.

• Aerospace Engineering and Technology
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• v.2 no.2
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• pp.1-10
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• 2003

An airship is statically unstable, because it has no wing, comparatively small tail and large hull. Hence, an accurate prediction of dynamic stability is critical. In this study, dynamic stability data of the Mid-Size Airship is acquired through forced oscillation wind tests. The test was done in BAR LAMP which is Birhle Applied Research Inc's facility located in Germany. The test was composed with 16 static runs and 26 dynamic runs. As a result, dynamic characteristics of the airship depends on sideslip angle, angular rate and its direction as well as angle of attack. Generally, it is obtained that 3 directional moments have damping, but normal force, side force, and cross-derivatives are unstable. The dynamic derivatives are not sensitive to control surfaces, but have nonlinear dependency on sideslip angle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.10 s.241
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• pp.1148-1155
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• 2005

In this study, the influence of changing combustor pressure on nitric oxide emission was investigated. Expansion of reaction region was more clear in the P$^{*}$ <1 conditions compared to the P$^{*}\geq1$ conditions, and it could be observed that flames are distinct in the P$^{*}\geq1$ conditions and that brightness is relative low and wide distribution is shown in the P$^{*}$ <1 conditions. In the respect of temperature distribution, narrow and high-temperature region was shown in the P$^{*}\geq1$ conditions. On the other hands, overall uniform temperature distributions were shown in the P$^{*}$ <1 conditions. Nitric oxide emission decreased with decreasing combustor pressure. This tendency was explained by the mean flame temperature distribution. Low NOx combustion is ascribed to wide-spread reaction region in the low combustor Pressure and oscillation were shown P$^{*}\leq0.97$, and strength and sizes of oscillation were more increased with lower pressure index. These results demonstrate that flame shape and nitric oxide emission can be controlled with changing combustor pressure.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.679-682
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• 2002

Energy dissipations in a general PHE flow are the compounded effects of the piled corrugate geometries and its wall pressure and temperature distributions. In addition, although the exchangers are substantial pieces of engineering equipment, they are composed of a very large number of nominally identical and small geometrical elements. In the present numerical study, the three-dimensionally complicated energy dissipation fields and those wall-shape-induced flow destabilization are investigated in the cross-corrugated passages, which result in high energy transports with comparatively low pressure drop. We revealed the critical conditions as $Re=157.3 for the wall-shape-induced flow destabilization in a general PHE element by initial value method, or shooting method, and compare its value to that of analytical solution of plane Poiseille flow, two-dimensional grooved flow and so on. We also observed the detailed variation of flow field and energy transportation with changes in time and flow variables such as Reynolds number. Lastly, we considered the flow natural frequency, or Strouhal number, with variation of hydrodynamic conditions for the best use of active control, such as forced mass flow rate pulsative flow, to enhance energy transportation.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.21-24
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• 2008

The present study numerically investigates the glottal airflow characteristics as well as acoustic features of phonation fully coupled with dynamic behavior of vocal folds. The vocal folds are described by a low-dimensional body-covered model characterized by bio-mechanical parameters such as glottal width, vocal folds stiffness, and subglottal pressure. The flow in the vocal tract is modeled as an incompressible, axisymmetric form of the Navier-Stokes equations (INS), while the acoustic field is predicted by the linearized perturbed compressible equations (LPCE). The computed result shows that a two-mass model of vocal folds is sufficient to reproduce temporal variations in oral airflow and glottis motion produced by female speakers. It is also found that i) the glottal width has a significant effect on the amplitude of glottal flow, and thus on the amplitude of acoustic wave in the vocal tract, ii) the vocal fold tension is the main control parameter for the fundamental frequency of phonation, iii) the subglottal pressure plays an appreciable role on reproduction of the self-sustained oscillation of vocal folds, and iv) the strength of pulsating airflow and vortical structures are primarily affected by glottal width and subglottal pressure, and are closely related to pitch, loudness, and voice quality. Finally, more comprehensive explanation about the difference between one- and two-mass models is presented with discussion of effectiveness of vocal folds oscillation and voice quality.