• Geomechanics and Engineering
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• v.34 no.3
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• pp.285-301
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• 2023

During the construction of E75 highway through Grdelica gorge in Serbia, a major failure occurred in the zone of reinforced rock slope. Excavation was performed in highly anisotropic Paleozoic schist rock formation. The reinforcement consisted of the two rows of micropile wall with pre-stressed anchors. Forces in anchors were monitored with load cells while benchmarks were installed for superficial displacement measurements. The aim of the study is to investigate possible causes of instability considering different probability distributions of the strength of discontinuities and anchor bond strength by applying different optimization techniques for finding the critical failure surface. Even though the deterministic safety factor value is close to unity, the probability of failure is governed by variability of shear strength of anisotropic planes and optimization method used for locating the critical sliding surface. The Cuckoo search technique produces higher failure probabilities compared to the others. Depending on the assigned statistical distribution of input parameters, various performance functions of the factor of safety are obtained. The probability of failure is insensitive to the variation of bond strength. Different sampling techniques should yield similar results considering that the sufficient number of safety factor evaluations is chosen to achieve converged solution.

• The Journal of the Acoustical Society of Korea
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• v.28 no.4
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• pp.363-369
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• 2009

In this paper, an estimation method is presented to determine the equivalent circuit model of an underwater acoustic piezoelectric transducer with multiple resonant modes. A fitness function that includes the coupled resonant effects is proposed to minimize an error between the measured impedance of the transducer and the calculated impedance of the equivalent model. Unknown parameters of the equivalent circuit are estimated by using PSO algorithm. The proposed method is applied to an example transducer of the sandwich type with 3 resonances in the frequency band of interest. The analytical impedance of the estimated equivalent circuit model is compared with the measured impedance of the transducer and the validity of proposed method is verified.

• Wind and Structures
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• v.38 no.5
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• pp.341-354
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• 2024

This paper presents a theoretical method to deal with the aerodynamic performance and pitch optimization of the horizontal axis wind turbine blades at low wind speeds. By considering a blade element, the functional relationship among the angle of attack, pitch angle, rotational speed of the blade, and wind speed is derived in consideration of a quasi-steady aerodynamic model, and aerodynamic loads on the blade element are then obtained. The torque and torque coefficient of the blade are derived by using integration. A polynomial approximation is applied to functions of the lift and drag coefficients for the symmetric and asymmetric airfoils respectively, where specific expressions of aerodynamic loads as functions of the angle of attack (which is a function of pitch angle) are obtained. The pitch optimization problem is investigated by considering the maximum value problem of the instantaneous torque of a blade as a function of pitch angle. Dynamic pitch laws for HAWT blades with either symmetric or asymmetric airfoils are derived. Influences of parameters including inflow ratio, rotational speed, azimuth, and wind speed on torque coefficient and optimal pith angle are discussed.

• International Journal of Control, Automation, and Systems
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• v.3 no.4
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• pp.640-645
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• 2005

Closed-loop model-free optimization of positive feedback time delay controllers for dominant time delay systems is presented. Iterative feedback tuning (IFT) is applied to the tuning of positive feedback time delay controller. Three experiments are carried out to perform the model-free gradient descent optimization. The initial controller parameters and duration in specifying the cost function are suggested. The effects of step size, filter function and time weighting function on the performance of the optimized controlled are given. Simulation and experimental studies are included to demonstrate the effectiveness of the tuning scheme.

• International Journal of Control, Automation, and Systems
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• v.4 no.6
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• pp.725-735
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• 2006

This paper deals with the problem of self-learning cooperative motion control for the pushing task of a humanoid robot in the sagittal plane. A model with 27 linked rigid bodies is developed to simulate the system dynamics. A simple genetic algorithm(SGA) is used to find the cooperative motion, which is to minimize the total energy consumption for the entire humanoid robot body. And the multi-layer neural network based on backpropagation(BP) is also constructed and applied to generalize parameters, which are obtained from the optimization procedure by SGA, in order to control the system.

• Tribology and Lubricants
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• v.20 no.5
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• pp.259-265
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• 2004

The sealing performance of O-rings is affected by working conditions such as applied pressure, operation temperature, pre-compressed ratio and material properties. In this paper, a pressurized and compressed elastomeric bi-polymer O-ring in which is inserted into a rectangular groove is analyzed by non-linear MARC finite element program based on the Taguchi experimental method. O-rings with 9 different profile models are analyzed for design parameters that are related to the diameter ratio between outer diameter and inner one of bi-polymer O-ring, compressive ratio, groove angle and groove depth. The calculated FEM results showed that the affection ratio of design parameter dlD, which may control sealing pressure of O-rings, is the most influential parameter among the groove angle, groove depth and compression ratio.

• Journal of the Korean Society of Safety
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• v.27 no.2
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• pp.57-64
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• 2012

For the vibration control of earthquake-excited buildings, an optimal design method of integrated control system considering soil-structure interaction is studied in this paper. Interaction between soils and the base of the building is simply modeled as lumped parameters and equations of motion are derived. The equations of motion are transformed into the state space equations and the probabilistic excitations such as Kanai-Tajumi power spectral density function is introduced. Then an optimization problem is formulated as finding hybrid or integrated control systems which minimizes the stochastic responses of the building structure for given constraints. In order to investigate the feasibility of the optimization method, an example design and numerical simulations are performed with tenstory building. Finally, numerical results are compared with a conventional design case that soil-structure interaction is not considered.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.5
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• pp.267-270
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• 2014

This paper presents the comparative performance of an adaptive FIR filter for a Delayed LMS algorithm. The delayed error signal was used to obtain a Delayed LMS algorithm to allow efficient pipelining for achieving a small critical path and area efficient implementation. This paper presents hardware efficient results (device utilization parameters) and power consumed. The FPGA families (Artix-7, Virtex-7, and Kintex-7) for a low voltage perspective are shown. The synthesis results showed that the artix-7 CMOS family achieves the lowest power consumption of 1.118 mW with 83.18 % device utilization. Different Precision strategies, such as the speed optimization and power optimization, were imposed to achieve these results. The algorithm was implemented using MATLAB (2013b) and synthesized on the Leonardo spectrum.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2281-2285
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• 2011

An algorithm for extracting SPICE MOS level 2 model parameters for the high voltage MOSFET DC model is proposed. The optimization method for analyzing the nonlinear data of the current-voltage curve using the Gauss-Newton algorithm is proposed and the pre-process step for calculating the threshold voltage and the mobility is proposed. The drain current obtained from the proposed method shows the maximum relative error of 5.6% compared with the drain current of 2-dimensional device simulation for the high voltage MOSFET.

• Journal of Applied Biological Chemistry
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• v.55 no.3
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• pp.149-156
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• 2012

The effects of solvent type and concentration, solid/liquid ratio, extraction time and repeated extraction on recovery of keratinase from solid-state fermentation (SSF) of chicken feather by a local Streptomyces sp. NRC 13S were investigated in order to establish the experimental conditions for keratinase yield. Among solvents tested, 0.5% (v/v) glycerol was the best. Box-Behnken design was used to investigate the effect of relevant variables on keratinase recovery. The factors investigated were solid/liquid ratio (1:1.66-1:6.66 g/mL), glycerol concentration (0.5-5% v/v) and repeated extraction (1-5 cycle). The results showed that the maximum recovery of keratinase (6933.3 U/gfs) was obtained using 0.5 (v/v) glycerol as extracting solvent, in a solid/liquid ratio of 1:5 and three extraction cycles.