• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.608-616
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• 2018

If a general nonlinear system is linearized by the successive multiplication of the 1st and 2nd order systems, then there are four types of poles in this linearized system: the pole of the 1st order system and the equal poles, two distinct real poles, and complex conjugate pair of poles of the 2nd order system. Linear Quadratic (LQ) control is a method of designing a control law that minimizes the quadratic performance index. It has the advantage of ensuring the stability of the system and the pole placement of the root of the system by weighted matrix adjustment. LQ control by the weighted matrix can move the position of the pole of the system arbitrarily, but it is difficult to set the weighting matrix by the trial and error method. This problem can be solved using the characteristic equations of the Hamiltonian system, and if the control weighting matrix is a symmetric matrix of constants, it is possible to move several poles of the system to the desired closed loop poles by applying the control law repeatedly. The paper presents a method of calculating the state weighting matrix and the control law for moving the equal poles with Jordan blocks to two real poles using the characteristic equation of the Hamiltonian system. We express this characteristic equation with a state weighting matrix by means of a trigonometric function, and we derive the relation function (${\rho},\;{\theta}$) between the equal poles and the state weighting matrix under the condition that the two real poles are the roots of the characteristic equation. Then, we obtain the moving-range of the two real poles under the condition that the state weighting matrix becomes a positive semi-finite matrix. We calculate the state weighting matrix and the control law by substituting the two real roots selected in the moving-range into the relational function. As an example, we apply the proposed method to a simple example 3rd order system.

• Korean Journal of Applied Biomechanics
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• v.17 no.3
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• pp.209-215
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• 2007

The purpose of this study was to investigate gait factor and muscle activity depending on hiking poles-using. Eight healthy men volunteered for this experiment. Each of them performed down-hill walking with hiking poles-using and without poles at speed of 3.5km/h for 45 minutes on a treadmill. The treadmill was set 25% down-hill inclination. Kinematic data collected in 60Hz were recorded and analyzed by using 2D motion capture system to measure step time and step length so on. And the lower extremity muscle activities were simultaneously recorded in 1500Hz and assessed by using EMG. The statistical analysis was the paired t-test with repeated measures to compare between hiking poles-using and without poles. The level of statistical significance for all tests was .05. The results of this study were following : Step time was showed statistically different according to pole conditions. That is, the case of poles-using was longer than without poles in step time. Also, step length was showed statistically different between two conditions. Step length about trials with poles was longer than trials without poles. In the muscle activity, the case of all muscles was not showed statistical significance about pole conditions. However, in most muscles IEMG, there were some decreasing-trend relatively when hiking polesusing.

• International Journal of Control, Automation, and Systems
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• v.5 no.2
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• pp.208-211
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• 2007

In a recently proposed method of model reduction for discrete interval systems, the denominator polynomial of a reduced model is computed by applying interval arithmetic to dominant poles of the original system. However, the denominator polynomial obtained via interval arithmetic usually has poles with larger intervals than desired ones. Hence an unstable polynomial can be derived from the stable polynomial. In this paper a simple technique is presented to partially overcome such a stability problem by accurately preserving desired real dominant poles.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.9
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• pp.35-44
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• 2014

This study was to secure the safety of poor appearance distribution concrete poles effectively and to reduce the replacement costs of them by developing a soundness evaluation index. The researcher of this study investigated poor appearance types of concrete pole, collected 53 of test samples, and tested pole strength. As a result of strength test, only 17 percent of poor appearance concrete poles were below 2.0 of safety factor spec. As results of multiple regression analysis, it is verified that surface air void, horizontal crack, net-shaped crack, elapsed year, vertical crack, and deterioration in concrete compressive strength have statistically negative effects on safety factor of concrete poles in a significant level. The researcher set up a soundness evaluation index by using multiple regression equation, and suggested that poor appearance concrete poles should be replaced or reinforced only in case of soundness evaluation score of 150 or above.

• Korean Journal of Applied Biomechanics
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• v.17 no.2
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• pp.1-9
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• 2007

Walking is not only an essential component of the human mobility, but also is a good exercise. Inability to walk freely can reduce an individual's quality of life and independence substantially. Being a relatively low impact activity, walking is particularly good for the elderly and research has shown that regular walking in the elderly reduces the chance of fall-related injuries and mental diseases as well. In spite of the documented benefits of regular walking, it is still difficult to walk without the aid of assistive devices for the frail elderly who have lower extremity problems. Assistive walking devices(AWD), such as crutches, canes, hiking-poles, T-Poles and walkers, are often prescribed to the elderly to make their walking be safe and efficient. Many researchers have demonstrated the effects of AWDs such as reducing lower extremity loading, improved dynamic/gait stability, yet, no study has been done for gait pattern when the elderly gait with AWDs. Therefore, the purpose of this study was to examine whether T-Poles, one of the AWDs, change the elderly gait pattern. Eight community-dwelling female elderly participated in this study. Laboratory kinematics during walking with T-Poles(PW) and with out T-Poles(NPW) was assessed. PW showed significant increase in step width, stride length, gait velocity and decrease in swing time. No significances were found in lower body joint angles but meaningful trend and pattern were found. Maybe the reason was due to the participants. Our participants were healthy enough so that the effect of T-Poles was minimum. PW also showed typical gait phases which are no single support phase during a gait cycle. It indicates that walking with T-Poles may guarantee safe and confident walking to the frail elderly.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.315-322
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• 2017

This study presents a novel two­phase eight stator poles and six rotor poles (8/6) switched reluctance machine (SRM) that can compensate for the vibration and noise problems of two­phase 6/3 SRM and compare the characteristics of two SRMs. In the case of two­phase 6/3 SRM, the short flux path and the flux direction inside the stator are not reversed, so they have high efficiency characteristics. However, the use of three rotor poles causes problems of vibration and noise because the radial force applied to the rotor poles is not balance. The proposed two­phase 8/6 SRM has advantages of 6/3 SRM such as the flux­reversal­free stator and it can improve vibration and noise by using six rotor poles due to balanced radial force acting on the rotor poles. In order to make a reasonable comparison between two SRMs, the electromagnetic field structure of 8/6 SRM is designed to have equivalent torque characteristic to 6/3 SRM and then the copper loss and core loss are compared and analyzed. Finally, we compare the effieicney of two SRMs using finite element analysis and compare the distribution of radial force acting on the rotor poles based on Maxwell's stress method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.125-127
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• 1996

This paper deals with the fabrication of 4 poles anisotropic Sr·ferrite plastic magnets. After Polyamide6 and polyamlde12 are kneaded respectively with Sr·ferrite powder, silane coupling and calcium stearate of lwt% are added for coating and pelleting. The pelleted specimen are injection-moulded under the magnetic field using 4 poles mould. For 4 poles anisotropic Sr·ferrite plastic magnets with polyamide6 as a binder, the surface magnetic flux density distribution is +943.8∼-943.87kG and the deviation is 5.2%, where as with polyamide12, the distribution is +1040.9∼-1040.9kG and the deviation is 5.4%. It shows that both of the magnet distributions are stable. As the results of the experiments, we find 4 poles anisotropic Sr·ferrite magnets have good properties as the materials appropriate for manufacturing magnet type synchronous motors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.566-572
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• 2021

A methodology for the identification and coordinates estimation of air cavities under urban ground or sandy soil using its natural poles and natural resonant frequencies is presented. The potential of this methodology was analyzed. Simulation models of PEC (Perfect Electric Conductor)s with various shapes and dimensions were developed using an EM (Electromagnetic) simulator. The Cauchy method was applied to the obtained EM scattering response of various objects from EM simulation models. The natural poles of objects corresponding to its instinct characterization were then extracted. Thus, a library of poles can be generated using their natural poles. The generated library of poles provided the possibility of identifying a target by comparing them with the computed natural poles from a target. The simulation models were made assuming that there is an air cavity under urban ground or sandy soil. The response of the desired target was extracted from the electromagnetic wave scattering data from its simulation model. The coordinates of the target were estimated using the time delay of the impulse response (peak of the impulse response) in the time domain. The MP (Matrix Pencil) method was applied to extract the natural poles of a target. Finally, a 0.2-m-diameter spherical air cavity underground could be estimated by comparing both the pole library of the objects and the calculated natural poles and the natural resonant frequency of the target. The computed location (depth) of a target showed an accuracy of approximately 84 to 93%.

• Korean Journal of Applied Biomechanics
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• v.19 no.2
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• pp.227-235
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• 2009

The purpose of this study was to analyze differences of 45minutes up-hill walking depending on hiking poles and steady walking time. Seven healthy men volunteered for this experiment. Each of them performed up-hill walking with hiking poles and without hiking poles at speed of 3.5km/h during 45minutes on a treadmill. The treadmill was set 25% up-hill inclination. The lower extremity 4 muscles activity including rectus femoris, tibialis anterior, gastrocnemius, biceps femoris was recorded and assessed by using EMG. And Heart rate(HR) and Rating of perceived exertion(RPE) were recorded and analyzed by 15minutes interval. The statistical analysis was two-way ANOVA with repeated measures to compare effects of hiking poles and steady walking time. The level of statistical significance for all tests was P<.05. The results of this study were following : Integrated EMG about four individual muscles doesn't have statistical significancy. However, the sum of IEMG of the four muscles was decreased some with poles than without poles(p<.0l) and IEMG about four muscles was rut different on steady walking time. Second, HR was increased significantly as time up(P<.01). RPE was decreased some with poles than without poles(P<.05) and RPE was increased significantly as time up(P<.01).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.92-97
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• 2014

The SRM is a doubly salient, singly excited machine. The torque is developed by the tendency for the magnetic circuit to adopt a configuration of minimum reluctance, i.e. for the rotor to move into in line with the stator poles and to maximize the inductance of the coils excited. It is common practice to combine them into groups of poles which are excited simultaneously; for example, 8/6 SRM (8 stator poles and 6 rotor poles) for 4 phases, 6/4, 12/8 SRM for 3 phases, 4/2, 6/3 SRM for 2 phases. Small number of phases in two-phase SRMs allows more cost savings with regards to the switching devices in the converter. The stator back irons of two phase 6/3 SRM and C-core 4/3 SRM does not experience any flux reversal as the flux is in the same direction whether phase A or B is excited. In this study, the similarities, the differences, and structural characteristics between the two SRMs was studied, The magnetic analysis also has been carried out by the finite element method analysis (FEM).