• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.609-617
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• 2016

Belt-driven Starter Generator (BSG) differs from other mild hybrid systems as the crankshaft of vehicle are not run off. Motor permits a low-cost method of adding mild hybrid capabilities such as start-stop, power assist, and mild levels of regenerative braking. Wound rotor synchronous motor (WRSM) could be adopted in BSG system for HEV e-Assisted application instead of the interior permanent magnet synchronous motor (IPMSM). In practice, adequate torque is indispensable for starter assist system, and energy conversion should be taken into account for the HEV or EV as well. Particularly, flux weakening control is possible to realize by adjusting both direct axis components of current and field current in WRSM. Accordingly, this paper present an off-line current acquisition algorithm that can reasonably combine the stator and field current to acquire the maximum torque, meanwhile the energy conversion is taken into consideration by losses. Besides, on account of inductance influence by non-uniform air gap around rotor, nonlinear inductances and armature flux linkage against current variation are proposed to guarantee the results closer to reality. A computer-aided method for proposed algorithm are present and results are given in form of the Look-up table (LUT). The experiment shows the validity of algorithm.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.20-27
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• 2017

This study investigated the problems in current practice of drive-train resonance analysis procedure and suggested solutions. The first problem is the resonance occurrence at the un-identified resonance point by the current practice, as for a solution the force spectrum analysis for each critical force transmitting component was suggested. The second one is the inaccurate estimation of potential resonance point in eigenfrequency analysis because of the non-consideration about the eigenfrequency dependency on rotor-speed, the fine linearization at each rotor speed point all over operational range was proposed to account for the affection. Lastly the insufficient time for resonance activation under run-up simulation condition was recognized as a problem in resonance load increasing analysis, as an alternative, steady state condition was suggested to estimate the maximum load increasing level.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.479-483
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• 1997

In general, motor parameters can be divided into mechanical/electrical parameters and harmonic parameters. Mechanical/electrical parameters identification of motor have been studying systematically for a long time. But, systematical study on harmonic parameters analysis for efficient motor drive system are very poor. The goal of this paper is to propose analyzing method of harmonic parameters for motor drive system with various experimental graphic screens and numerical results and to develope harmonic parameters analyzer. A developed analyzer is made up 586-PC and DSP (digital signal processor) board, motor drive system, power and harmonic parameters analyzing software for windows. Harmonic parameters are analyzed using correlation signal processing techniques based on the correlation between voltage and current waveforms. Analysis results are visualized by 3-D current coordinates, and it is compared and evaluated with conventional time/frequency domain. To verify the validity of the proposed system, 1/4HP capacitor run type single phase induction motor and thyristor speed controller is used for analyzing. Harmonic parameters of motor drive system is analyzed and verified, with varying fire angle of thyristor speed controller, and the proposed approach is to confirm validity.

• The Journal of the Korea Contents Association
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• v.8 no.5
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• pp.134-144
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• 2008

A city is the center of all the economic activities, politics, administration and creation of cultures, and it is also a social community. It is also an environment in which human beings live and act, and thus, psychological and emotional pleasure are greatly demanded. Facilities of cities, buildings and harmonizing each and every structures with the environment sets up the image and the identity of a city because they are the most important visual structuring elements in cityscapes. Currently, most of the cities in Korea including Seoul, are in discordance with their natural environment because of all different sorts of buildings and signboards are jumbled up close together. The traditional, local colors have disappeared form those cities and all cities look the same. It is hard to find traditional beauty and identities of the cities in Korea, and the Korean cities are not even close to the threshold of other foreign cities. In order to solve these problems, there is a dire need of improving the modification of cityscapes in the long run. This research aims to understand the current abstruse situation Korean cities are in, analyze their problems and describe actual methods of improving those cities so that they can have a more ordered and organized structures. Also, this research should be used as a data of future researches based on citiscapes.

• Analytical Science and Technology
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• v.28 no.5
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• pp.309-316
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• 2015

The analytical method of lead in plasma by ICP-MS was validated after securing environment within class 1,000 classification. We tested specificity and accuracy of within-run and between-run. According to measurement of the amount of suspended particulates in a clean room, 0.3~62 particles were detected in 0.3 µm size while 0.0~28.3 particles were observed in 0.5 µm size. Total suspended particulates met required environment with up to 90.3 particles. The MDL (Method detection limit) of the sample which has been fabricated using fetal bovine serum (FBS) blank was 1.77 ng/L, and LOQ (Limit of quantification) was 5.55 ng/L. The slope, intercept and correlation coefficient of the calibration curve were y=1.09×10⁻³x+4.88×10⁻² and r=0.9999, which showed good correlation. The specificity, within-run and between-run accuracy satisfied the standard at more than 50 ng/L. The average lead concentration in plasma of the general people, current workers and retired workers was 55.4 ng/L, 440 ng/L, and 132 ng/L.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.186-196
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• 2017

In order to resolve the trimming difficulty in rotor CFD calculations, a high-efficiency and improved "delta trim method" is established to compute the blade control settings that are necessary to identify the blade motion. In this method, a simplified model which combines the blade element theory and different inflow models is employed to calculate the control settings according to the target aerodynamic forces, then it is coupled into a CFD solver with unsteady Navier-Stokes equations by the delta methodology, which makes the control settings and aerodynamics calculated and updated in the meantime at every trim cycle. Different from the previous work, the current research combines the inflow model based on prescribed wake theory. Using the method established, the control settings and aerodynamic characteristics of Helishape 7A, AH-1G and Caradonna-Tung rotors are calculated. The influence of different inflow models on trimming calculations is analyzed and the computational efficiency of the current "delta trim method" is compared with that of the "CFD-based trim method". Furthermore, for the sake of improving the calculation efficiency, a novel acceleration factor method is introduced to accelerate the trimming process. From the numerical cases, it is demonstrated that the current "delta trim method" has higher computational efficiency than "CFD-based trim method" in both hover and forward flight, and up to 70% of the amount of calculation can be saved by current "delta trim method" which turns out to be satisfactory for engineering applications. In addition, the proposed acceleration factor shows a good ability to accelerate the trim procedure, and the prescribed wake inflow model is always of better stability than other simple inflow models whether the acceleration factor is utilized in trimming calculations.

• Ocean Systems Engineering
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• v.6 no.1
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• pp.23-60
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• 2016

The major objective of this study was to develop further understanding of 3D nearshore hydrodynamics under a variety of wave and tidal forcing conditions. The main tool used was a comprehensive 3D numerical model - combining the flow module of Delft3D with the WAVE solver of XBeach - of nearshore hydro- and morphodynamics that can simulate flow, sediment transport, and morphological evolution. Surf-swash zone hydrodynamics were modeled using the 3D Navier-Stokes equations, combined with various turbulence models (${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES). Sediment transport and resulting foreshore profile changes were approximated using different sediment transport relations that consider both bed- and suspended-load transport of non-cohesive sediments. The numerical set-up was tested against field data, with good agreement found. Different numerical experiments under a range of bed characteristics and incident wave and tidal conditions were run to test the model's capability to reproduce 3D flow, wave propagation, sediment transport and morphodynamics in the nearshore at the field scale. The results were interpreted according to existing understanding of surf and swash zone processes. Our numerical experiments confirm that the angle between the crest line of the approaching wave and the shoreline defines the direction and strength of the longshore current, while the longshore current velocity varies across the nearshore zone. The model simulates the undertow, hydraulic cell and rip-current patterns generated by radiation stresses and longshore variability in wave heights. Numerical results show that a non-uniform seabed is crucial for generation of rip currents in the nearshore (when bed slope is uniform, rips are not generated). Increasing the wave height increases the peaks of eddy viscosity and TKE (turbulent kinetic energy), while increasing the tidal amplitude reduces these peaks. Wave and tide interaction has most striking effects on the foreshore profile with the formation of the intertidal bar. High values of eddy viscosity, TKE and wave set-up are spread offshore for coarser grain sizes. Beach profile steepness modifies the nearshore circulation pattern, significantly enhancing the vertical component of the flow. The local recirculation within the longshore current in the inshore region causes a transient offshore shift and strengthening of the longshore current. Overall, the analysis shows that, with reasonable hypotheses, it is possible to simulate the nearshore hydrodynamics subjected to oceanic forcing, consistent with existing understanding of this area. Part II of this work presents 3D nearshore morphodynamics induced by the tides and waves.

• Journal of Applied Tourism Food and Beverage Management and Research
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• v.10
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• pp.187-202
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• 1999

We desperately recognize from the economic situation in IMF crisis that only competive goods and serviced. It is anticipated that this difficult situation will probably be continued till 1999. Therefore, it is necessary to think over real aspects of eating=outdoors in IMF period and to provide an opportunity to confront with this crisis. Analysis a recent tendency of domestic eating-outdoors business, there appears, first of all, dual types of eating-outdoors; the one is a sort of 'Cost Sale', which provides some special menu with lowest prices, and the other is a type of 'Family Restaurant', which regards the atmosphere of the place as one of the most essential elements. Both types are getting more popular today. As the result, neither of the alternative cannot recover the current Depression. It is natural that no other conditions can compete with good tastes, fancy atmosphere, and good prices. As a matter of fact, however, it is quite difficult to run this type of bussiness adjusted the above whole conditions. Therefore owners of eating-house must decide to run either ' Cost Sale' or 'Family Restaurant' first and investigate some problems and conditions accordingly. In ane way, the owner intensively visits to some eating houses which is similar style in size and management to that of his style in size and management to that of his and look over what is good and what is bad Right after this investigation, it is efficient for he or she to improve his or her business style in size and management in a short period. It is helpful to check some complements; improvement of signboards, cleaning up of the interior, selecting suitable menu, adjusted prices, tastes, and service quality etc. Although eating-outdoors business is hard hit by IMF, We hope that it would rapidly be brisk in 2000, becaused by that time the basis of each industry would be high qualified, and rich technology would be accumulated.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.3
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• pp.146-153
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• 2010

When the production run is short and process parameters change frequently, it is difficult to monitor the process using traditional control charts. In such a case, the coefficient of variation (CV) is very useful for monitoring the process variability. The CV control chart is an effective tool to control the mean and variability of process simultaneously. The CV control chart, however, is not sensitive at small shifts in the magnitude of CV. The CV-EWMA(exponentially weighted moving average) control chart which was developed recently is effective in detecting a small shifts of CV. Since the CV-EWMA control chart scheme can be viewed as a weighted average of all past and current CV values, it is very sensitive to small change of mean and variability of the process. In this paper, we propose an FIR(Fast initial response) CV-EWMA control chart to improve the sensitivity of a CV-EWMA scheme at process start-up or out-of-control process. Moreover, we suggest the values of design parameters and show the results of the performance study of FIR CV-EWMA control chart by the use of average run length(ARL). Also, we compared the performance of FIR CV-EWMA control chart with that of the CV-EWMA control chart and we found that the CV-EWMA control chart gives longer in-control ARL and much shorter out-of-control ARL.

• Journal of Korea Multimedia Society
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• v.13 no.1
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• pp.1-9
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• 2010

Today's growth of the mobile communication infrastructure made mobile computing systems like cellular phones came next to or surpassed the desktop PCs in popularity due to their mobility. Although the performance of mobile devices is now being improved continuously, it is a current common sense that compute intensive large-scale applications can hardly run on any kind of mobile handset devices. To clear up this problem, we decided to exploit the mobile cluster computing system and surveyed the existing ones first. We found out, however, that most of them are not the actual implementations but a mobile cluster infrastructure proposal or idea suggestions for reliable mobile clustering. To make cell phones participated in cluster computing nodes, in this paper, we propose a redesigned JPVM cluster computing engine and a set of WIPI mobile runtime functions interfacing with it. And we also show the performance evaluation results of real parallel applications running on our Mobile-JPVM cluster computing systems. We find out by the performance evaluation that large-scale applications can sufficiently run on mobile devices such as cellular phones when using our mobile cluster computing engine.