• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.26-30
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• 2001

Up to now, Most studies of hydroelasticity are about frequency domain analysis. Those aren't suited for analysis of the landing take-off, and dropping of aircraft on a structure. So, the concern of this paper is the transient behavior of a VLFS subjected to dynamic load, induced by airplane landing and take-off. To predict the added mass, damping coefficient, and wave exciting force, the source-dipole distribution method was used in the frequency domain. The responses are accomplished by using the FEM scheme. A time domain analysis method is based on the Newmark β method to pursue the time step procedure, taking advantage of memory effect function for hydrodynamic effects.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.1
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• pp.33-40
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• 2014

Reliability analysis of jacket type offshore wind turbine (OWT) support structure under extreme ocean environmental loads was performed. Limit state function (LSF) of OWF support structure is defined by using structural dynamic response at mud-line. Then, the dynamic response is expressed as the static response multiplied by dynamic response factor (DRF). Probabilistic distribution of DRF is found from response time history under design significant wave load. Band limited beta distribution is used for internal friction angle of ground soil. Wind load is obtained in the form of thrust force from commercial code called GH_Bladed and then, applied to tower hub as random load. In a numerical example, the response surface method (RSM) is used to express LSF of jacket type support structure for 5MW OWF. Reliability index is found using first order reliability method (FORM).

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.559-567
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• 2018

In this paper, we propose a new load forecasting method for smart air conditioning (A/C) based on the modified thermodynamics of indoor temperature and the unbiased finite memory estimator (UFME). Based on modified first-order thermodynamics, the dynamic behavior of indoor temperature can be described by the time-domain state-space model, and an accurate estimate of indoor temperature can be achieved by the proposed UFME. In addition, a reliable A/C load forecast can be obtained using the proposed method. Our study involves the experimental validation of the proposed A/C load forecasting method and communication construction between DR server and HEMS in a test bed. Through experimental data sets, the effectiveness of the proposed estimation method is validated.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.11
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• pp.655-662
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• 1999

This paper describes controller design and simulation-model development of a dynamic voltage compensator using series and shunt inverters. The control system was designed using PI controller and vector relationship between the supply voltage and load voltage. A simulation model with EMTP was developed to analyze performance of the controller and the whole system. The simulation and experiment results confirm that the dynamic compensator can restore the load voltage under the fault of the distribution system, such as single-line-ground fault, three-line-to-ground fault, and line-to-line fault.

• IE interfaces
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• v.19 no.1
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• pp.1-8
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• 2006

The mobile communication network has to offer good quality of services (QoS), high capacity, and more coverage at a lower cost. However, with the increase of cellular user, the shortage of capacity due to unbalanced call distribution and lack of QoS are common. This paper deals with dynamic sectorization for efficient resource management to solve load unbalancing among microcells in CDMA (Code Division Multiple Access) microcellular system. Dynamic load balancing can be effected by grouping micro-cells properly and grouping can be developed through a routing mechanism. Therefore, we use ants and their routes to choose the optimum grouping of micro-cells into sectors using Multiple Ant Colony System (MACS)in this paper.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.83-92
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• 2008

This paper develops the theory for a fault-tolerant, permanent magnet biased, homopolar magnetic bearing. If some of the coils or power amplifiers suddenly fail, the remaining coil currents change via a novel distribution matrix such that the same magnetic forces are maintained before and after failure. Lagrange multiplier optimization with equality constraints is utilized to calculate the optimal distribution matrix that maximizes the load capacity of the failed bearing. Some numerical examples of distribution matrices are provided to illustrate the theory. Simulations show that very much the same dynamic responses (orbits or displacements) are maintained throughout failure events (up to any combination of 3 coils failed for the 6 pole magnetic bearing) while currents and fluxes change significantly. The overall load capacity of the bearing actuator is reduced as coils fail. The same magnetic forces are then preserved up to the load capacity of the failed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.2
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• pp.199-208
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• 2012

This paper proposes a quasi Z-source DVR(Dynamic Voltage Restorer) system with a series connection of the output terminals, to compensate the voltage variations in the 6.6[kV]/60[Hz] power distribution system. The conventional DVR using one quasi Z-source AC-AC converter has the advantage which it can compensate the voltage variations without the need for the additional energy storage device such as a battery, but it is impossible to compensate for the 50[%] under voltage sags. To solve this problem, a DVR system using two quasi Z-source AC-AC converters with the series connection of the output terminals is proposed. By controlling the duty ratio D in the buck-boost mode, the proposed system can control the compensation voltage. For case verification of the proposed system, PSIM simulation is achieved. As a result, in case that the voltage sags-swells occur 10[%], 20[%], 60[%] in power distribution system, and, in case that the 50[%] under voltage sags-swells continuously occur, all case could compensate by the proposed system. Especially, the compensated voltage THD was examined under the condition of the 10[%]~50[%] voltage sags and the 20[${\Omega}$]~100[${\Omega}$] load changes. The compensated voltage THD was worse for the higher load resistances and more severe voltage sags. Finally, In case of the voltage swells compensation, the compensation factor has approached nearly 1 regardless of the load resistance changes, while the compensation factor of voltage sags was related to the load variations.

• Advances in aircraft and spacecraft science
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• v.10 no.1
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• pp.19-49
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• 2023

The present study proposes a theoretical and numerical investigation on the dynamic response behaviour of a functional graded (FG) ceramic-metal tapered rotor shaft system, by the differential quadrature finite elements method (DQFEM) to identify the natural frequencies for modelling and analysis of the structure with suitable validations. The purpose of this paper is to explore the influence of heat gradients on the natural frequency of rotation of FG shafts via three-dimensional solid elements, as well as a theoretical examination using the Timoshenko beam mode, which took into account the gyroscopic effect and rotational inertia. The functionally graded material's distribution is described by two distribution laws: the power law and the exponential law. To simulate varied thermal conditions, radial temperature distributions are obtained using the nonlinear temperature distribution (NLTD) and exponential temperature distribution (ETD) approaches. This work deals with the results of the effect on the fundamental frequencies of different material's laws gradation and temperature gradients distributions. Attempts are conducted to identify adequate explanations for the behaviours based on material characteristics. The effect of taper angle and material distribution on the dynamic behaviour of the FG conical rotor system is discussed.

• Journal of information and communication convergence engineering
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• v.3 no.1
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• pp.13-17
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• 2005

The link e daggregation between 10GbE switches requires an advanced framistribution method to be properly and efficiently applied. The fixed or dynamic frame distribution methods, formerly proposed, cannot fully utilize the aggregated links, where the receiving terminal only attaches to a pre-specified link among multiple physical links. A frame distribution method using padding is proposed for the link aggregation between 10GbE switches to solve this problem. We compared the performance of the proposed method with those of the static and dynamic frame distribution methods. As a result, the proposed method shows a better performance when the offered load is below 0.7 and the average length of the frames is longer than 954 bytes.

• Journal of the Semiconductor & Display Technology
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• v.4 no.2 s.11
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• pp.25-32
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• 2005

This paper proposes a method for the intelligent load distribution of two cooperating robots(TCRs) using fuzzy logic. The proposed scheme requires the knowledge of the robots' dynamics, which in turn depend upon the characteristics of large flat panel displays(LFPDs) carried by the TCRs. However, the dynamic properties of the LFPD are not known exactly, so that the dynamics of the robots, and hence the required Joint torque, must be calculated for nominal set of the LFPD characteristics. The force of the TCRs is an important factor in carrying the LFPD. It is divided into external force and internal force. In general, the effects of the internal force of the TCRs are not considered in performing the load distribution in terms of optimal time, but they are essential in optimal trajectory planning; if they are not taken into consideration, the optimal scheme is no longer fitting. To alleviate this deficiency, we present an algorithm for finding the internal-force (actors for the TCRs in terms of optimal time. The effectiveness of the proposed system is demonstrated by computer simulations using two three-joint planner robot manipulators.