• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.102-109
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• 2013

In this paper, a new torque predictive control method of interior permanent magnet synchronous motor is developed based on an extended rotor flux. Also, a duty ratio prediction method is proposed and allows the duty ratio of the active stator voltage vector to be continuously calculated. The proposed method makes it possible to relatively reduce the torque ripple under the steady state as well as to remain the good dynamic response in the transient state. With the duty ratio prediction method, the magnitude and time interval of the active stator voltage vector applied can be continuously controlled against the varying operation conditions. This paper shows a comparative study among the switching table direct torque control(DTC), the SVM-DTC, conventional torque predictive control, and the proposed torque predictive control. Simulation results show validity and effectiveness of this work.

• Proceedings of the Technology Innovation Conference
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• 2001.06a
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• pp.117-130
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• 2001

R&D is the core competence of an enterprise. Furthermore, R&D requires huge capital investment and has very risky characteristics. Therefore, to be successful in R&D process, several approaches of engineering economics are used prior to decision-making. Until now, typical approaches of engineering economics such as NPV(net present value) or DCF(Discounted cash flow) have been used. But, they cannot properly capture managerial flexibility to adapt and revise later decisions in response to unexpected market development. In a constantly changing and always uncertain marketplace, managerial operation flexibility and strategic adaptability have become vital in order to successfully capitalize on favorable future investment opportunities and limit losses from adverse market development. For the alternatives of conventional static decision-making approaches, new concept of using real options is introduced. Real option theory is based on financial option's characteristics and checks every revision interval whether situation have changed favorable to decision maker or not. In advantageous situation, the decision maker has only to go on. In contrast, with unfavorable situation, he abandons the investment immediately. In this aspect, real option model is more suitable in very uncertain and dynamic business environment in that it can provide the opportunity to cope with flexibility. This paper suggests efficient and effective R&D investment strategy by using real options model. In addition, this paper compares financial options and real options.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.605-612
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• 2008

The shear wave velocity ($V_s$) has been commonly used to evaluate the dynamic properties of soil. The field $V_s$ probe (FVP) was already developed to assess the shear stiffness of a soft clay. The objective of this study is to investigate the disturbance effects of the FVP due to the penetration. The laboratory tests are conducted in a large-scale consolidometer (calibration chamber). The reconstituted clay is mixed at the water content of 110% using a slurry mixer. The FVP and down-hole test are carried out every 1cm interval to compare the data. In addition, two square rods with transducers are also implemented to get the reference value. The shear waves evaluated by the FVP, dow-hole tests, and reference rods are closely matched. This study suggests that the disturbance effect of the FVP due to the penetration into the soft clay soils is small enough and the $V_s$ evaluated by the FVP reflects well the in-situ characteristics. Furthermore, the combination of the FVP and down-hole test shows the possibility of hybrid equipment.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.91.2-91.2
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• 2012

Kokubun (1983) reported the local time variation of normalized amplitude of sudden commencement (SC) with a strong day-night asymmetry at geosynchronous orbit with 81 SC events. Further careful inspection of Kokubun's local time distribution reveals that the normalized SC amplitudes in the prenoon sector are larger than those in the postnoon sector. That is, there is a morning-afternoon asymmetry in the normalized SC amplitudes. Until now, however, there are no studies on this SC-associated morning-afternoon asymmetry at geosynchronous orbit. Motivated by this previous observation, we investigate a large data set (422 SC events in total) of geosynchronous SC observations and confirm that the geosynchronous SC amplitudes is larger in the morning sector than in the afternoon sector. This morning-asymmetry is probably caused by the enhancement of partial ring current, which is located in the premidnight sector, due to solar wind dynamic pressure increase. We also examine the latitudinal and seasonal variations of the normalized SC amplitude. We find that the SC-associated geosynchronous magnetic field perturbations are dependent on the magnetic latitude and season of the year. This may be due to the location of the magnetopause and cross-tail currents enhanced during SC interval with respect to geosynchronous spacecraft position.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.1
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• pp.117-129
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• 2009

The bullwhip effect is known as the significant factor which causes unnecessary inventory, lost sales or cost increase in supply chains. Therefore, the causes of the bullwhip effect must be examined and removed. In this paper, we develop two analytical tools for the bullwhip effect control in supply chains. First, we develop the quantitative models for computing the bullwhip effect in a three-stage supply chain consisted of a single retailer, a single distributor and a single manufacturer when the fixed-interval replenishment policy is applied at each stage. The quantitative models are developed under the different conditions for the demand forecasting and share of customer demand information. They are validated through the computational experiments. Second, we develop a simulation-based decision support system for the bullwhip effect control in a more diverse dynamic supply chain environment. The system includes a what-if analysis function to examine the effects of varying input parameters such as operating policies and costs on the bullwhip effect.

• Korean Journal of Applied Biomechanics
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• v.28 no.3
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• pp.193-197
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• 2018

Objective: The relationship between the rest intervals during physical tasks and performance enhancement has been studied. However, whether or not different rest intervals would result in altered multiplanar ankle kinematics during performance of the Star Excursion Balance Test (SEBT) is unknown. Method: Fifteen healthy subjects (7 males and 8 females) without a history of ankle injuries were participated in this study. 3 rest intervals of 10, 20, and 40 seconds were used during the current study. Three visits were required in order to complete the 3 rest intervals. Variables of interest included dorsiflexion (DF) excursion, tibial internal rotation (TIR), and eversion (EV) excursions. The means of ankle angular excursions were compared across the 3 directions in the 3 rest interval groups. Results: There were no significant main effects for any variables between restintervals. However, DF excursion in the anteromedial (AM) direction was greaterthan in both the medial (M) and posteromedial (PM) directions and was greater in the M direction compared to the PM direction. TIR excursion in the AM direction was less than in both the M and PM directions. Conclusion: Different rest intervals ranging from 10 to 40 seconds did not influence ankle angular excursions during the SEBT in a healthy population. However, our results suggest that multiplanar motion is necessary during the SEBT and differs depending on the direction of movement.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.2
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• pp.108-119
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• 1999

In this paper, a three phase PWM AC to DC boost converter that operates with unity power factor and sinusodial input currents si presented. The current control of the converter is based on the space vector PWM strategy with fixed switching frequency and the imput current tracks the reference current within one sampling time interval. Space vector PWM strategy for current control was materialized as a digital control method by using DSP. By using this control strategy low ripples in the output voltage, low harmonics in the input current and fast dynamic responses are achieved with a small capacitance in the dc link.

• Annals of Clinical Neurophysiology
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• v.7 no.1
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• pp.13-16
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• 2005

Background: The purpose of this study is to investigate the effect of the intensive functional electrical stimulation(FES) on the improvement of the gait pattern of the chronic hemiplegic patients. Method: Six hemiplegic patients, who could walk independently but have equinovarus deformity during the gait cycle, participated in this study. The affected peroneus longus and tibialis anterior muscles of all subjects were stimulated for 2 weeks period (20 minutes duration, 6 times/day). We measured the activities (mean voltage) of those muscles during the walking, using dynamic EMG. Results: After treatment, there were significant improvements in the strength of peroneus longus and tibialis anterior muscles and the gait speed, but there was no interval change of the spasticity of plantar flexor. The mean voltages of two muscles are significantly increased in all the patients (p<0.05). Conclusion: The results showed that the intensive FES on affected peroneus longus and tibialis anterior muscles in chronic hemiplegic patients could be useful for the improvement of functional gait.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.5
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• pp.82-91
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• 2011

In this paper, a planar model for mechanics of a vehicle/pedestrian collision incorporating road gradient is derived to evaluate the pre-collision speed of vehicle. It takes into account a few physical variables and parameters of popular wrap and forward projection collisions, which include horizontal distance traveled between primary and secondary impacts with the vehicle, launch angle, center-of-gravity height at launch, distance from launch to rest, pedestrian-ground drag factor, the pre-collision vehicle speed and road gradient. The model including road gradient is derived analytically for reconstruction of pedestrian collision accidents, and evaluates the vehicle speed from the pedestrian throw distance. The model coefficients have physical interpretations and are determined through direct calculation. This work shows that the road gradient has a significant effect on the evaluation of the vehicle speed and must be considered in accident cases with inclined road. In additions, foreign/domestic empirical cases and multibody dynamic simulation results are used to construct a least-squares fitted model that has the same structure of the analytical one that provides an estimate of the vehicle speed based on the pedestrian throw distance and the band within which the vehicle speed would be expected to be in 95% of cases.

• Journal of Environmental Science International
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• v.13 no.10
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• pp.891-902
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• 2004

In order to predict air pollution and Yellow-sand dispersion precisely, it is necessary to clarify the sensitivity of meteorological field input interval. Therefore numerical experiment by atmospheric dynamic model(RAMS) and atmospheric dispersion model(PDAS) was performed for evaluating the effect of temporal and spatial resolution of meteorological data on particle dispersion. The results are as follows: 1) Base on the result of RAMS simulation, surface wind direction and speed can either synchronize upper wind or not. If surface wind and upper wind do not synchronize, precise prediction of Yellow-sand dispersion is strongly associated with upwelling process of sand of particle. 2) There is no significant discrepance in distribution of particle under usage of difference temporal resolution of meteorological information at early time of simulation, but the difference of distribution of particles become large as time goes by. 3) There is little difference between calculated particles distributions in dispersion experiments with high temporal resolution of meteorological data. On the other hand, low resolution of meteorological data occur the quantitative difference of particle density and there is strong tendency to the quantitative difference.