• International Journal of Fuzzy Logic and Intelligent Systems
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• v.2 no.3
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• pp.220-226
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• 2002

In this paper, we develop the intelligent digitally redesigned fuzzy controller for nonlinear systems. Takagi-Sugeno (TS) fuzzy model is used to model the nonlinear systems and a continuous-time fuzzy-model-based controller is designed based on the extended parallel-distributed-compensation(EPDC) method . The digital controllers are determined from existing analogue controllers. The proposed method provides an accurate and effective method for digital control of continuous-time nonlinear systems and enables us to efficiently implement a digital controller via the pre-determined continuous-time 75 fuzzy-model-based controller. We have applied the proposed method to the duffing forced oscillation system to show the effectiveness and feasibility of the proposed method.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.524-526
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• 1999

In the construction of successful fuzzy models and/or controllers for nonlinear systems, the identification of a good fuzzy inference system is an important yet difficult problem, which is traditionally accomplished by a time-consuming trial-and-error process. In this paper, we propose a systematic identification procedure for complex multi-input single-output nonlinear systems with DNA coding method. A DNA coding method is optimization algorithm based on biological DNA as conventional genetic algorithms(GAs) are. The strings in the DNA coding method are variable-length strings, while standard GAs work with a fixed-length coding scheme. the DNA coding method is well suited to learning because it allows a flexible representation of a fuzzy inference system. We also propose a new coding method fur applying the DNA coding method to the identification of fuzzy models. This coding scheme can effectively represent the zero-order Takagi-Sugeno(TS) fuzzy model. To acquire optimal TS fuzzy model with higher accuracy and economical size, we use the DNA coding method to optimize the parameters and the number of fuzzy inference system. In order to demonstrate the superiority and efficiency of the proposed scheme, we finally show its application to a Duffing-forced oscillation system.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.12-23
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• 2021

In the conventional experiment to assess the towing operations, the towing stability of the towed vessel has been evaluated under the condition without lateral motion of the tug-boat. However, the tug-boats may have a lateral force to change the direction of the towed vessel. In this study, experiments have been conducted considering unsteady conditions in the towing system. First, a towing test system in a Circular Water Channel (CWC) using the conventional experimental method is built. Second, the towing characteristics of the towed vessel are investigated using the conventional method, and they are compared with other research results and stability discriminant criteria. Third, the lateral motion of the tug-boat was modeled as a sinusoidal motion using a forced oscillation device changing frequency and amplitude. Finally, the discussion is given in terms of both towing- and course-stability of the towed vessel according to the lateral motion of the tug-boat.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.4 s.142
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• pp.368-378
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• 2005

The effects of rotary oscillation on the unsteady laminar flow past a circular cylinder. are numerically investigated in the present study. The numerical solutions for the 20 Wavier-Stokes equation are obtained using a finite volume method Tn the framework of an overlapping grid system. The vortex formation behind a circular cylinder and the hydrodynamics of wake flows for different rotary oscillation conditions are analyzed from the results of numerical simulation. The lock-on region is defined as the region that the natural shedding frequency due to the Karmann Vortex shedding and the forcing frequency due to the forced oscillating a cylinder are nearly same, and the quasi-periodic states are observed around that region. At the intersection between lock-on and non-lock-on region the shedding frequency is bifurcated. After the bifurcation, one frequency fellows the forcing frequency($S_f$) and the other returns to the natural shedding frequency($St_0$). in the quasi-periodic states, the variation of magnitudes and relevant phase changes of $C_L$ with forcing phase are examined.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.311-314
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• 2006

This paper concerns about total dynamic analysis of integrated mining system. This system consists of vertical steel pipe, intermediate buffer station, flexible pipe and self-propelled miner. The self-propelled miner and buffer are assumed as rigid-body of 6-dof. Discrete models of vertical steel pipe and flexible pipe are adopted, which are obtained by means of lumped-parameter method. The motion of mining vessel is not considered. Instead, the motion of mining vessel is taken into account in form of various boundary conditions (e.g. forced excitation in slow motion and/or fast oscillation and so on). A terramechanics model of extremely soft cohesive soil is applied to the self-propelled miner. The hydrodynamic forces and moments are included in the dynamic models of vehicle and lifting pipe system. Hinged and fixed constraints are used to define the connections between sub-systems (vertical steel pipe, buffer, flexible pipe, miner). Equations of motion of the coupled model are derived with respect to the each local coordinates system. Four Euler parameters are used to express the orientations of the sub-systems. To solve the equations of motion of the total dynamic model, an incremental-iterative formulation is employed. Newmark-b method is used for time-domain integration. The total dynamic responses of integrated mining system are investigated.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.1
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• pp.117-125
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• 2012

This paper presented the design of SRPS, ground function test, and the deployment test on a high speed taxi of KC-100 airplane. KAI has developed a spin recovery system in collaboration with Airborne Systems for KC-100 general aviation airplane. Spin mode analysis, rotary balance and forced oscillation tests were performed to obtain the rotational, dynamic derivatives in the preliminary design phase. Prior to the detailed design process of SRPS, approximations for initial estimation of design parameters- fineness ratio, parachute porosity, parachute canopy filling time, and deployment method- were considered. They were done based on the analytical disciplines such as aerodynamics, structures, and stability & control. SRPS consists of parachute, tractor rocket assembly for deployment, attach release mechanism (ARM) and cockpit control system. Before the installation of SRPS in KC-100 airplane, all the control functions of this system were demonstrated by using SBTB(System Breakout Test Box) in the laboratory. SBTB was used to confirm if it can detect faults, and simulate the firing of pyrotechnic devices that control the deployment and jettison of SRPS. Once confirmed normal operation of SRPS, deployment and jettison of parachute on the high speed taxiing were performed.

• Tuberculosis and Respiratory Diseases
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• v.45 no.2
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• pp.351-359
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• 1998

Background: The effects of exercise on pulmonary function are complex and have been the subject of many investigations. But, there has been disputes about the effect of exercise on spirometric parameters and there is no study about the effect of exercise on IOS(Impulse Oscillometry)parameters. IOS, a new method of pulmonary function test, is based on the relationship between the pressure and flow oscillation which is produced by applying sinusoidal pressure oscillation to the respiratory system via the mouth. Method: Fifty-nine young adults without respiratory symptoms were divided into three groups according to degree of exercise(hard exercise group: mean exercise time is over three hours per week at least for the last one month, light exercise group : between thirty minutes to three hours, nonexercise group : less than thirty minutes) and undertaken pulmonary function test(simple spirometry and IOS). Results: The effects of exercise on spirometric parameters; percentage of predictive value of forced vital capacity(FVC % pred) was higher in hard exercise group than nonexercise group(hard exercise group: $102.4{\pm}14.8$, nonexercise group: $93.7{\pm}9.9$, p=0.017), but there was no significant difference in percentage of predicted value of forced expiratory volume in one second(FEV 1 % pred) and percentage of predicted value of forced expiratory flow 50% (FEF 50% pred) between groups. The effects of exercise on IOS parameters: Reactance at 5Hz(X5) was significantly lower in hard exercise group than nonexercise group(hard exercise group: $-0.166{\pm}0.123hPa/1/s$, nonexercise group: $-0.093{\pm}0.036hPa/1/s$, p=0.006) but there was no significant difference in central resistance(Rc), peripheral resistance(Rp), resonance frequency(RF) and resistance at 5Hz, 20Hz between groups. Conclusion: Hard exercise increased FVC % pred on spirometric parameters and decreased reactance at 5Hz(X5) on IOS parameters.

• Journal of Navigation and Port Research
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• v.42 no.1
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• pp.1-8
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• 2018

This study covers the selection of systems measuring the behaviour of the slender structure in the underwater environment and its performance assessment. From a comparison of an instrumentation system that can measure the continuous behaviour along the entire length of the slender structure, the underwater camera system is finally selected as the most appropriate semi-permanent measurement system for Deep-sea Ocean Engineering Basin of KRISO. An experiment on the rigid pipes for a basic performance evaluation of the underwater camera is conducted in this study. The motion of a top excited rigid pipe is measured with the utilization of the underwater camera system. The performance of the underwater camera is evaluated by comparing the movement of a pipe measured by the underwater camera with the measured input signals. Through the top excitation experiment for the slender structure, the real-time three-dimensional measurement of the underwater camera system is qualitatively evaluated in this case. The developed underwater camera system can apply to the system to measure dynamic behaviour of a slender structure and mooring line in Deep Ocean Engineering Basin.

• Journal of Navigation and Port Research
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• v.34 no.3
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• pp.195-203
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• 2010

This paper concerns about total dynamic analysis of integrated mining system. This system consists of vertical steel pipe, intermediate buffer station, flexible pipe and self-propelled miner. The self-propelled miner and buffer are assumed as rigid-body of 6-dof. Discrete models of vertical steel pipe and flexible pipe are adopted, which are obtained by means of lumped-parameter method. The motion of mining vessel is not considered. Instead, the motion of mining vessel is taken into account in form of various boundary conditions (e.g. forced excitation in slow motion and/or fast oscillation and so on). A terramechanics model of extremely cohesive soft soil is applied to the self-propelled miner. Hinged and ball constraints are used to define the connections between sub-systems (vertical steel pipe, buffer, flexible pipe, self-propelled miner). Equations of motion of the coupled model are derived with respect to the each local coordinates system. Four Euler parameters are used to express the orientations of the sub-systems. To solve the equations of motion of the total dynamic model, an incremental-iterative formulation is employed. Newmark-${\beta}$ method is used for time-domain integration. The total dynamic responses of integrated mining system are investigated.

• Clinical and Experimental Pediatrics
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• v.50 no.9
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• pp.862-867
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• 2007

Purpose : The impulse oscillometry (IOS) is applicable to young children because it requires minimal cooperation and a non-invasive method to measure the mechanics of respiratory system. This study aimed to develop the reference values in school-aged children in Korea, using IOS which is a modification of forced oscillation technique (FOT). Methods : Measurements were performed in 92 previously untrained healthy children, aged 7 to 12 years old, using IOS. We analyzed the relationships between the data about their age, height, weight, body surface area (BSA), body mass index (BMI) and the result of IOS using the linear regression test. Results : The success rate of IOS was 92.4%. Stepwise multiple regression of resistance of respiratory system (Rrs) and reactance of respiratory system (Xrs) in natural form for age, height, weight, BSA, BMI showed that height was the most significant predictor and altogether of 5 variables explained the Rrs and Xrs most. Our regression equations at multiple frequencys were comparable to published reference values, especially about the Rrs obtained at 5 Hz. Conclusion : IOS is a feasible method to measure the respiratory resistance in untrained children. We got the reference values using IOS and it seems to be useful to diagnose a variety of respiratory diseases.