• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.3
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• pp.186-189
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• 2003

Various empirical formulas have been developed to describe the stability of breakwater armor stones. The Hudson formula is known to have needs to be refined in many ways. but it is most widely used because of its simplicity. The van der Meer formula is sometimes used for the cross-check, but it is not very popularly used due to its complexity and the uncertainty of the relevant parameters. Recently, on the other hand, Yoo(2003) proposed a formula of a simple form using a new non-dimensional number which is called 'action slope' (abbreviated as Yoo formula hereinafter). In this study, in order to provide coastal engineers with some idea of the use of these formulas, their accuracies were estimated by comparing with the experimental data reported by van der Meer in 1987 and 1988. It was found that the van der Meer formula showed the highest accuracy, while the Hudson formula of very low accuracy needed considered judgment on its use. On the other hand, the Yoo formula of slightly lower accuracy but simpler expression than the van der Meer formula seems to be able to be used in engineering practice if a slightly higher safety factor is taken.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.81-87
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• 2010

In order to calculate the accurate runoff from a basin, nonlinearity in the relationship between rainfall and runoff has to be considered. Many runoff calculation models assume the linearity in the relationship or are too complicated to be analyzed. Therefore, the storage function method has been used in the prediction of flood because of the simplicity of the model. The storage function method has five parameters with related to the basin and rainfall characteristics which can be estimated by the empirical trial and error method. To optimize these parameters, regression method or optimization techniques such as genetic algorithm have been used, however, it is not easy to optimize them because of the complexity of the method. In this study, the metamodel is proposed to estimate those model parameters. The metamodel is the combination of artificial neural network and genetic algorithm. The model is consisted of two stages. In the first stage, an artificial neural network is constructed using the given rainfall-runoff relationship. In the second stage, the parameters of the storage function method are estimated using genetic algorithm and the trained artificial neural network. The proposed metamodel is applied in the Peong Chang River basin and the results are presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1163-1168
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• 1999

This paper proposes a wireless positioning method using the CDMA mobile communicaton network. The proposed method is time-based positioning method that uses mobile-station arrival time of forward link signal from base-stations. In this mehtod there are TDOA and TOA methods that use time-difference-of-arrival and time-of-arrival, respectively. Error characteristics and implementation simplicity of the two methods are compared and analyzed each other. As a results, it showed that TDOA has advantage of less sensitivity to the time error compared to TOA but has disadantage of more sensitivity to the spatial error. Also, from architecture of the CDMA system that is time synchronized to only active base-station it is analyzed that adoption of TDOA method is more advantageous than TOA because time difference of signal arrival from the neighbor base-stations against the active base-station can be measured more easily. Therefore, conclusion is made that TDOA is beat suit to the time-based positioning method for the present CDMA mobile communication networkgorithm performs block-by-block coherent decoding with the aid of pilot symbols. It is shown that the complexity of the algorithm grows linearly as a function of sequence length. The performance of the algorithm is shown to better than that of the conventional pilot symbol aided (PSI) algorithm. Simulation results are presented to assess the performance of the algorithm and the results are compared with that of the conventional PSI alforithm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.5
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• pp.981-989
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• 2010

In this study, we introduce a new architecture of fuzzy inference system. In the fuzzy inference system, we use Fuzzy C-Means clustering algorithm to form the premise part of the rules. The membership functions standing in the premise part of fuzzy rules do not assume any explicit functional forms, but for any input the resulting activation levels of such radial basis functions directly depend upon the distance between data points by means of the Fuzzy C-Means clustering. As the consequent part of fuzzy rules of the fuzzy inference system (being the local model representing input output relation in the corresponding sub-space), four types of polynomial are considered, namely constant, linear, quadratic and modified quadratic. This offers a significant level of design flexibility as each rule could come with a different type of the local model in its consequence. Either the Least Square Estimator (LSE) or the weighted Least Square Estimator (WLSE)-based learning is exploited to estimate the coefficients of the consequent polynomial of fuzzy rules. In fuzzy modeling, complexity and interpretability (or simplicity) as well as accuracy of the obtained model are essential design criteria. The performance of the fuzzy inference system is directly affected by some parameters such as e.g., the fuzzification coefficient used in the FCM, the number of rules(clusters) and the order of polynomial in the consequent part of the rules. Accordingly we can obtain preferred model structure through an adjustment of such parameters of the fuzzy inference system. Moreover the comparative experimental study between WLSE and LSE is analyzed according to the change of the number of clusters(rules) as well as polynomial type. The superiority of the proposed model is illustrated and also demonstrated with the use of Automobile Miles per Gallon(MPG), Boston housing called Machine Learning dataset, and Mackey-glass time series dataset.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.123-128
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• 2012

In order to overcome the hardware complexity and performance limit problems, recently the multi-core architecture has been prevalent. For hardware simplicity, usually RISC processor is adopted as the unit core processor. However, if the performance of unit core processor is enhanced, the overall performance of the multi-core processor architecture can be further enhanced. In this paper, in-order superscalar processor is utilized as the core for the multi-core processor architecture. Using SPEC 2000 benchmarks as input, the trace-driven simulation has been performed for the number of superscalar cores between 2 and 16 and the window size of 4 to 16 extensively. As a result, the 16-core superscalar processor for the window size of 16 results in 8.4 times speed up over the single core superscalar processor. When compared with the same number of cores, the multi-core superscalar processor performance doubles that of the multi-core RISC processor.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.800-807
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• 2016

We propose a fast algorithm using Extreme Contour Point (ECP) to detect the angle of rotated images, is implemented by rotation feature of one covered frame image that can be applied to correct the rotated images like in image processing for real time applications, while CORDIC is inefficient to calculate various points like high definition image since it is only possible to detect rotated angle between one point and the other point. The two advantages of this algorithm, namely compatibility to images in preprocessing by using Sobel edge process for pattern recognition. While the other one is its simplicity for rotated angle detection with cyclic shift of two $1{\times}n$ matrix set without complexity in calculation compared with CORDIC algorithm. In ECP, the edge features of the sample image of gray scale were determined using the Sobel Edge Process. Then, it was subjected to binary code conversion of 0 or 1 with circular boundary to constitute the rotation in invariant conditions. The results were extracted to extreme points of the binary image. Its components expressed not just only the features of angle ${\theta}$ but also the square of radius $r^2$ from the origin of the image. The detected angle of this algorithm is limited only to an angle below 10 degrees but it is appropriate for real time application because it can process a 200 degree with an assumption 20 frames per second. ECP algorithm has an O ($n^2$) in Big O notation that improves the execution time about 7 times the performance if CORDIC algorithm is used.

• Korean Journal of Human Ecology
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• v.13 no.2
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• pp.271-282
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• 2004

The purposes of this study were to research the behavior of consumption and needs about the female university students to provide useful information which would help finding the marketing source of cosmeceuticals. The sample was consisted of 464 female university students who had experiences of using the cosmeceuticals. Data were analyzed by factor analysis, frequency, x2-test, t-test, ANOVA(LSD) using SPSSWIN. The results were as follows: When the female university students purchased the cosmeceuticals, they considered the effectiveness and the price, so were satisfied with good effect and low price. The most important marketing methods in cosmeceuticals for female university students were through the internet and mail order shopping. Whereas, demerit factors of internet shopping were founded to be the complexity of exchange or refund and the little chance of free samples for trial. The good marketing strategies might be sending trial samples, future payment system after trial period, and/or supporting the event held in the university. Besides, it might be a consideration to have an event for the improvement by public trial. Anti-aging cosmeceutical was the most preferred item for female students, sun protection and whitening cosmetics next in order. Therefore, a target customer for cosmeceuticals might be lowered in age. The purchasing cost system and therapeutic effect of cosmeceuticals had to be developed for 20's. It was necessary to be safe and effective. The factors affecting the level of satisfaction for cosmeceuticals could be categorized into 4; market environment, simplicity of purchase, product merit and additional service. The needs for cosmeceuticals showed significant differences according to grade and kinds of product.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.529-534
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• 2014

Pyrotechnic devices are widely used for space appendages. However, a cube satellite requirements do not permit the use of explosive pyrotechnic device. A nichrome burn wire release has typically been used for holding and release of deployable appendages of the cube satellite due to its simplicity and low cost. However, relatively low mechanical constraint force and system complexity for application of multi-deployable systems are disadvantages of the conventional mechanism. To overcome these drawbacks, we developed a hinge driving segmented nut type holding and release mechanism based on the nichrome burn wire release. The functional performance of the mechanism has been verified through release function test, static load test and shock level measurement test.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8C
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• pp.712-719
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• 2007

In this paper, we propose a new, effective, fast motion estimation algorithms using $4{\times}4$ pixels Hadamard transform. The Hadamard transform has the advantage of simplicity because it uses only addition and subtraction. Motion estimation is composed of three stages. First, it should be decided whether to terminate the search early and use a previous motion vector with DC(Direct Current) coefficients. Then the adaptive matching scan order for motion estimation should be determined according to the image complexity using AC(Alternating Current) coefficients. Experimentally, we adapted this algorithms to MVFAST and PMVFAST algorithms, and the proposed algorithms turn out to be very efficient in terms of computational speed while remaining almost the same in terms of PSNR(Peak Signal-to-Noise Ratio) compared to MVFAST and PMVFAST algorithms.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1223-1228
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• 2011

A moving-coil type linear actuator has been widely used in the system reciprocating short stroke because of its several advantages, such as the structural simplicity, low weight and a fast control response speed. This paper presents a design approach for improving the actuating performance with a clear expression of optimal configuration represented by a level set function. The optimization problem is formulated to minimize the variation of magnetic force at every moving displacement of the mover for fast and easy control. To consider the manufacturability of actuator, the concept of phase-field model is incorporated to control the complexity of structural boundaries. To verify the usefulness of the proposed method, the core design example of cylindrical linear actuator is performed.