• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.105-111
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• 2003

Wheel for passenger car support the car weight with tires, and they transmit rolling and braking power into the ground. Whittling away at wheel weight is more effective to boost fuel economy than lighting vehicle body structure. A shape of hole in disk is optimized for minimizing the weight of steel wheel. Pro/ENGINEER program is used for formulating the design model, and ANSYS package is selected for analyzing the design model. It has difficulties to interface these commercial software directly. For Combining both programs, response surface methodology is applied to construct approximation functions for maximum stresses and maximum displacements are obtained by full factorial design of five levels. This steel wheel is modeled in 14-inch diameter of rim, and wide parameter of hole in disk is only selected as design variable for reducing the weight of steel whee. PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm, which used the second-order information in the direction finding problem and uses the active set strategy, is used for solving optimization problems.

• Structural Engineering and Mechanics
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• v.74 no.2
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• pp.157-173
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• 2020

In the finite element modelling of long-span cable-stayed bridges, there are a lot of uncertainties brought about by the complex structural configuration, material behaviour, boundary conditions, structural connections, etc. In order to reduce the discrepancies between the theoretical finite element model and the actual static and dynamic behaviour, updating is indispensable after establishment of the finite element model to provide a reliable baseline version for further analysis. Traditional sensitivity-based updating methods cannot support updating based on static and dynamic measurement data at the same time. The finite element model is required in every optimization iteration which limits the efficiency greatly. A convenient but accurate Kriging surrogate model for updating of the finite element model of cable-stayed bridge is proposed. First, a simple cable-stayed bridge is used to verify the method and the updating results of Kriging model are compared with those using the response surface model. Results show that Kriging model has higher accuracy than the response surface model. Then the method is utilized to update the model of a long-span cable-stayed bridge in Hong Kong. The natural frequencies are extracted using various methods from the ambient data collected by the Wind and Structural Health Monitoring System installed on the bridge. The maximum deflection records at two specific locations in the load test form the updating objective function. Finally, the fatigue lives of the structure at two cross sections are calculated with the finite element models before and after updating considering the mean stress effect. Results are compared with those calculated from the strain gauge data for verification.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.320-324
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• 2015

Optimization of the fabrication process of NiO-yttrium doped barium zirconate (BZY) composite anode substrates using tape-casting for high performance thin-film protonic ceramic fuel cells (PCFCs) is investigated. The anode substrate is composed of a tens of microns-thick anode functional layer laminated over a porous anode substrate. The macro-pore structure of the anode support is induced by micron-scale polymethyl methacrylate (PMMA) pore formers. Thermal gravity analysis (TGA) and a dilatometer are used to determine the polymeric additive burn-out and sintering temperatures. Crystallinity and microstructure of the tape-cast NiO-BZY anode are analyzed after the sintering.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1093-1102
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• 2010

Principal component analysis (PCA) is a well-known method for dimension reduction while maintaining most of the variation in data. Although PCA has been applied to many areas successfully, it is sensitive to outliers. Several variants of PCA have been proposed to resolve the problem and, among the variants, robust fuzzy PCA (RF-PCA) demonstrated promising results. RF-PCA uses fuzzy memberships to reduce the noise sensitivity. However, there are also problems in RF-PCA and the convergence property is one of them. RF-PCA uses two different objective functions to update memberships and principal components, which is the main reason of the lack of convergence property. The difference between two functions also slows the convergence and deteriorates the solutions of RF-PCA. In this paper, a variant of RF-PCA, called RF-PCA2, is proposed. RF-PCA2 uses an integrated objective function both for memberships and principal components. By using alternating optimization, RF-PCA2 is guaranteed to converge on a local optimum. Furthermore, RF-PCA2 converges faster than RF-PCA and the solutions found are more similar to the desired solutions than those of RF-PCA. Experimental results also support this.

• Journal of Information Technology Services
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• v.14 no.3
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• pp.183-196
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• 2015

The concept of energy-efficient networking has begun to spread in the past few years, gaining increasing popularity. A common opinion among networking researchers is that the sole introduction of low consumption silicon technologies may not be enough to effectively curb energy requirements. Thus, for disruptively boosting the network energy efficiency, these hardware enhancements must be integrated with ad-hoc mechanisms that explicitly manage energy saving, by exploiting network-specific features. The IEEE 802.3az Energy Efficient Ethernet (EEE) standard is one of such efforts. EEE introduces a low power mode for the most common Ethernet physical layer standards and is expected to provide large energy savings. However, it has been shown that EEE may not achieve good energy efficiency because mode transition overheads can be significant, leading to almost full energy consumption even at low utilization levels. Coalescing techniques such as packet coalescing and interrupt coalescing were proposed to improve energy efficiency of EEE, but their implementations typically adopt a simple policy that employs a few fixed values for coalescing parameters, thus it is difficult to achieve optimal energy efficiency. The paper proposes adaptive interrupt coalescing (AIC) that adopts an optimal policy that could not only improve energy efficiency but support performance. AIC has been implemented at the sender side with the Intel 82579 network interface card (NIC) and e1000e Linux device driver. The experiments were performed at 100 M bps transfer rate and show that energy efficiency of AIC is improved in most cases despite performance consideration and in the best case can be improved up to 37% compared to that of conventional interrupt coalescing techniques.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.9
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• pp.759-768
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• 2016

Design and performance analysis of propeller for solar-powered HALE UAV, EAV-3 are conducted. Experiment points of design variables are obtained by using Design of Experiment(DOE) and Kriging meta-model is generated for objective and constraints function. The geometry of propeller is designed by evaluating the response surface with requirement and restrictions. The validity of the design is verified by meta-model based optimization. Computational analyses are carried out by using commercial CFD code and the results are compared with those from a design code and wind tunnel test. The results showed good agreement with predictions of the design code at the design altitude. Also, it is confirmed that the blockage effect due to the measurement device and support strut is included in the test data and the results including this effect compare well with the test data.

• Journal of KIISE:Databases
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• v.30 no.4
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• pp.362-371
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• 2003

In this paper, we propose an optimal interest point extraction method to support shape-base image classification and indexing for image database by applying a dynamic threshold that reflects the characteristics of the shape contour. The threshold is determined dynamically by comparing the contour length ratio of the original shape and the approximated polygon while the algorithm is running. Because our algorithm considers the characteristics of the shape contour, it can minimize the number of interest points. For n points of the contour, the proposed algorithm has O(nlogn) computational cost on an average to extract the number of m optimal interest points. Experiments were performed on the 70 synthetic shapes of 7 different contour types and 1100 fish shapes. It shows the average optimization ratio up to 0.92 and has 14% improvement, compared to the fixed threshold method. The shape features extracted from our proposed method can be used for shape-based image classification, indexing, and similarity search via normalization.

• Journal of KIISE:Information Networking
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• v.29 no.4
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• pp.386-396
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• 2002

This paper presents a neural network-based near-optimal routing algorithm. It employs a modified Hopfield Neural Network (MHNN) as a means to solve the shortest path problem. It uses every piece of information that is available at the peripheral neurons in addition to the highly correlated information that is available at the local neuron. Consequently, every neuron converges speedily and optimally to a stable state. The convergence is faster than what is usually found in algorithms that employ conventional Hopfield neural networks. Computer simulations support the indicated claims. The results are relatively independent of network topology for almost all source-destination pairs, which nay be useful for implementing the routing algorithms appropriate to multi -hop packet radio networks with time-varying network topology.

• Journal of Korean Society of Forest Science
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• v.101 no.1
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• pp.1-6
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• 2012

To achieve the forest fire management goals such as early detection and quick suppression, fire resources should be allocated at high probability area where forest fires occur. The objective of this study was to develop and validate models to estimate spatially distributed probabilities of occurrence of forest fire. The models were builded by exploring relationships between fire ignition location and forest, terrain and anthropogenic factors using logistic regression. Distance to forest, cemetery, fire history, forest type, elevation, slope were chosen as the significant factors to the model. The model constructed had a good fit and classification accuracy of the model was 63%. This model and map can support the allocation optimization of forest fire resources and increase effectiveness in fire prevention and planning.

• Journal of Wetlands Research
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• v.17 no.2
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• pp.155-162
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• 2015

This study was conducted to assess the removal characteristics of taste and odor causing compounds(2-MIB and geosmin) and micro organic matters. GAC and BAC process consisting of Ozone/AOP and activated carbon was applied. As a result, the influent concentration of 2-MIB 159 ng/L and geosmin 371 ng/L were removed 42% and 86% by ozone 1.0 mg/L, and 58%, 90% by AOP(ozone 1.0 mg/L + $H_2O_2$ 0.5 mg/L). Also it showed less than 2 ng/L effluent in GAC process and 99.8% removal efficiency in BAC process. Therefore, BAC process combining ozone/AOP and GAC is effective for persistent removal of micro organic matters, taste and odor. It is needed for optimization of Ozone/AOP process according to influent concentrations.